First off, I have never dealt with this behaviour in a horse before and I've raised this one from birth.  There is no reason for this to start but it has.  He had colic surgery Oct 2019 and I got to ride him 3 days before the C-19 shut down.  He was turned out in pasture.. 

You know when horses bolt as soon as you take the halter off no matter how hard you try to hold them or you try to unhalter calmly so they just walk away... This is what he's doing.  He's doing it when bridling and letting him go in a stall or pasture.  When bridling I have to slip it under the rope halter and off again. 

Now last week at home he decided to do it when I went to get on. Halter was off, reins over his neck and ready to get on, he suddenly spun and bolted in a dead run. 

Truly I feel like I need to work his hind end into the ground 3x a day but time with a new human baby hasn't permitted that just yet.  So I'm looking for suggestions if that's not what would fix it anyways. 

Man, thats kind of a hard one!! So weird he has learned that since you have raised him since birth. If you had bought him like that , it would make you wonder how he got that way. The only thing I can think of to try would be to hobble him. Maybe if he learns his feet can't move it would help??? 

That's a great idea.  He is super smart and really is an A-hole..  He knows he can get away with it and now he really knows he can.  He's one that will set back unless he knows it's something that will hurt instead. He's always been this way with jerk tendencies. 

Hobbles are a great idea if it teaches him

but now (although it was the last time I tried to ride this weekend at home) he bolts when I go to get on.  Not sure how to do that with hobbles

I think if I remember something from a horsemanship clinic, the idea is you make the motion to take the halter off, then when you feel that surge like he's going to bolt, get tough and make him back up as many steps as you feel like making him.  You have to keep doing this until he begins to dread that backing up, then one day he'll quit.  Worked with a horse I had who liked to get excited and rear up when I wasn't walking him to where we were headed fast enough.  (what can I say, he was an Easy Jet) 

I remember you, by the way, as an oldie on this board and a really wild pic of you turning a barrel.  Loved it.

I'm not sure how everyone on here feels about Clinton Anderson, but I use his videos to work on issues I have with my horses. In one of his videos, he talks about removing the halter, but not taking it completely off (leaving it around the horse's neck) and he makes sure the horse keeps its attention on you, even after the halter is off, until you remove it completely. (It's kind of hard to explain, but I can look for the video if you're interested!) Maybe go back to work in a round pen (so he can't run far if he gets away) and work on this after lounging? I hope you get it figured out!

True!! The getting on would not be a good idea hobbled. As they say, the A-holes make tough horses. LOL From what I understand, Kristie Petersons' BOZO was a massive A-hole. I heard that sometimes someone would have to ear him down so she could get on. LOL. ANd shots were a big NO as well. My mom went to the NFR on a big horse that if you didn't run your hand down his leg to put boots on he WOULD kick your head in. LOL Vets could NOT wear the bib overalls they worse back in the day or he would bolt!! He would also Bolt if he was tied to be shod. If he wasn't tied, he was fine. I wonder if your horse got hung up with a lead rope once when you didn't see it? Let us know how it works out. 

At risk of taking crap

i spranged my ankle but still needed to turn the biggest Ahole horse I have ever had out in the pasture.  I could not deal with his bolting or trying to fix him with my ankle the size of a grapefruit.  I brought a pail with feed in it. Sat it down gave him a bite and took his halter off while he was chewing. I walked away he quietly finished than turned around half quiet and loped away to play.  
totally fixed him I was just hoping to survive long enough for my ankle to get better but I stopped needing the pail after about 10 times

It's a respect issue. I bet you have babied him and treated him like a pet.

I would try those manna Pro Apple nuggets treats, let him know that he'll get a sweet reward here and there when he dont haul booty once you take the halter or bridle off, I would keep some in my pockets so they would be handy when you feel a reward coming on. . But the mounting part I dont know, never had to deal with that, and it could became dangerous if you get hung up on him. 

I had a mare that would bolt at barrel races when bridled. It ended up she had kissing spine. 

We got the round pen put up yesterday and I worked him until his head came down. I had him come to me, took the halter off, he stood, I stepped back and waited and he didn't move. I stepped back up to him and waited and then showed him the halter which he tried to put his head in so I pet on him and we  quit there. I'm going to try this for awhile and see if he's just fresh from the over a year long break or this is a true issue..  I'll keep y'all posted! 

even now on all my horses I do tip their nose around when I mount and I would think if you pulled his nose around like a colt you should be able to get on him and he would circle you..........

he does sound smart...............just be careful cause you have a baby to think about..........

interesting.........

I didn't read all the comments, so maybe this was suggested above.  Try a collar as well as your halter.  That way he is never loose when bridling, always tied.  I use two leadropes, one for the halter and one for the collar.  Unhalter, bridle, then unsnap the collar.  The collar just stays on, doesn't get in the way of your headgear in any way when riding.  I had a hard time finding a collar, but it has worked very well.

Mine started doing this after he was treated for EPM. My horse never had any quirks, easy to get along with and a pleasure to deal with. Now he has to wear a neck rope when tied and a chain across his nose when leading around or he just takes a wild hair and darts off. He respects the chain and the neck rope, so far.

I would look for the reason he is doing this. Horses don't understand "respect", that is a prefrontal cortex thing and while ours is sizeable, the horse's is almost nonexistent. If he was a good guy before, then there is a reason and most often it's a pain thing or at the very least a discomfort thing. Also kind of seems like he got used to the work free pasture life and understandably doesn't want to go back to work. Give him a reason to want to work/be with you. Could be as easy as giving a couple cookies/a little feed beforeand after you unhalter him. Handgrazing and just hanging out with no agenda will help, too. 

Just a thought. Put a clinton anderson halter on him. Then put a regular halter over it. Have a good hold of that c.a. halter when you take the regular one off. When he goes to take off, jerk him hard & firmly tell him NO. Do this over & over again untill he gets the point. I also agree with the poster who suggested round pen work. 

The day a horse arrives on my place it begins learning to stand stone still until I 'release' it. EVERY TIME I pull the halter off -- in the stall, pasture, wherever, that horse must stand stone still until I 'release'. I always loop the lead around their neck prior to pulling a halter or bridle. That becomes their cue it is time to be stone still.  Sometimes it takes a few weeks, but you must be consistent in making them stand stone still. Sometimes we stand there for 10 minutes. It takes some work, but it is worth it. I expect my farrier to respect my method and to always make the horses stand still a minute or two prior to release after he is done. He does it because he appreciates the fact I have spent time making my horses safe and easy to shoe -- so much so that I do not have to be there for him to shoe. I demand and expect good manners from every horse on the place.  It's about consistency in how you do it and doing it the same every time --- short cuts will get you killed. 

I also make my horses back away from the stall door when I enter their stall -- they go to the other side and stay there while I pour feed in their bucket or place hay. They stay there until I release them.

They learn to stand like a rock at the mounting block.  If they don't stand at the block quietly, they get their butt worked off on the longe line. The mounting block is a nice, quiet  place to rest.  All learn to get in the trailer when I walk them up and point inside.  I teach all to ground tie.

As someone else said, it's about respect, but you earn that respect with consistent cues and handling behavior.  In all my 50+ years with horses I have never had one that could not learn to be still and do what I asked.  So often we are rushed and in such a hurry to get them rode, exercised, etc.,  that we do take time to make the horse be still, listen and mind us.  As I said, that will get you killed.  When with your horse, slow down, do what is right to assure you have a safe, enjoyable horse. 

Maybe respect is not the right word.   Maybe him running off on you is he thinks you are below him in the pecking order of the herd.   There is no equal with horses.  You are dominate over him or he is dominate over you.

Have you just left the halter and lead on him and let him drag it around?  Him stepping on it and having to pay attention to it a few days may give him more respect for you.  I'd personally tie the halter (with his bit over it) to his tail and work him about 10 minutes each side. Keep his feet moving and make him uncomfortable all while he's saddled.  If he stands then get on him.  If he bolts then do this again both sides untill he realizes that having his nose tied to his tail sucks.  An arena or big paddock is best, a round pen is to small of an area.  Him moving and turning and turning and turning is the goal.  Good luck!