Don’t know if I would get any help off of here or not but I’ll ask anyway.

Basically I’ve noticed that if I’m sat down anywhere and im sitting up straight my whole back is shaking, but when I slouch down in the process of slouching down my back just jerks a couple of times and then I’m fine as soon as I’m slouching, no more shaking or jerking... I was wondering if I’d get any help off of here I’d ask my doctors but it takes forever to get an appointment... if anybody could help me that would be great? X