I don't know....I do tend to really curl up into a ball and sit sideways on the couch and rest the side of my head on the back of the couch - or hide my face behind my hands.

For me, it just feels like a way of protecting myself. It's not conscious when I do it, but I have had T try to get me to sit up, put my feet on the floor, etc when I'm getting too lost in whatever made me curl up in the first place. I tend to do it when I'm in a really young place.

I have no idea if it's common, etc - but that is my experience...