I'm with my hedgie right now and she was just doing the bouncy thing a few minutes ago. She is a little over six months and I started noticing her doing that about three months ago. I notice she does it whenever she is getting ready to go to sleep. I too have asked what that is, but no one seems to know. I wouldn't worry too much about it. Doesn't seem to be bothering your little hedgie. I'll let you know if I find anything else out about it.