I have also have the same problem! I really found that walking them into a wall or stopping them into a wall is helpful. Another thing that you can do is after your ride, fiddle or move around in the saddle. My horse is a lot calmer once we are done riding. I like bending over, taking my feet out of the sturuips and putting them back in, teaching them that they should stand still unless I ask them to move.
Hope this helps!
I’m having the exact same issue but what is working for me so far is getting someone else to stand her still then slowly get them to hold her lightly then eventually not at all to the point where I am holding her and she’s not moving also consistently plays a big role the more you get her to stay still and give praise,the better!
Hope this helps