Could be an itch, could be tapping your heels together, stretching arms, anything at all. 

I've just noticed recently that whenever I'm in an uncomfortable situation, or certain things are a bit more triggering, I will itch the back of my neck. When things get worse and my other personalities start getting upset (especially during switching) I also move my head around a lot. The popping of my neck as well as hands is very satisfying during those situations. It's something to do and fidget with, keeping me a bit more sane for a few minutes. 

Just curious how common this is.