It's normal with the spider morph. The genetics that create the spider look also have some kind of influence with the nervous system. No one is exactly sure what the link is. It varies a lot between specimens....some show little-to-no outward signs...some spin their whole bodies with no ability to control it. Most fall somewhere between those two extremes. It can get better or worse as they mature. Some grow out of it...some get worse. Stress can make it more noticeable.