This is something of concern and you should speak to your psychiatrist about it and see what they can do to stop it and see what the cause is.
I agree you should talk to your doctor. When you get this way is it high anxiety? I remember when I was taking that med that gave me sever panic attacks my entire body would stiffen up. I would have to grip onto something and stretch my arms and legs out straight as waves of panic washed over me, and it felt like my entire body was freezing. I couldn't explain it. Even when I was not having these I was always tapping my feet or fidgeting. At first I didn't even think it was the med since I had so much other emotion stress in my life at that time, but after about two weeks I looked it up and sure enough, panic attacks was a side effect. I went straight to my doctor, (even though he was an OB GYN he took me right off of it.) Well, after about a week those went away. So, talk to your doctor ASAP. You don't need to live with that if they can figure out what is causing it.