Has anyone else's baby ever have "shivers" or "shakes"?

My 9 month old "shivers" like he's got a chill about 5 or 6 times a day. It is not when he pees either. For a few days there it happened like 20 or 30 times but just those 3 days. He is extremely smart and has no developmental delays. He has just learned to crawl and I wonder if it somehow coincided with that. This only happens when he sits straight up.