I just realized - this isn't the first time I moved involuntarily while I was already active. A couple months ago I crashed a maintenance cart into a pole at work because my leg suddenly jerked and hit the gas before I could put the cart into reverse, and it took about 30 seconds to regain control of my leg after I hit the pole. I was reduced to yelling at it before it would move again. I had to come up with an excuse to my boss for how I could crash a cart that way without it being on purpose... I don't think "my leg refused to obey me" would fly. At first I was terrified that something was really wrong with me, but then decided since I didn't get enough sleep the night before, that must have been the reason.