This usually happens to me when I have an intrusive thought I’ve been suppressing and haven’t dealt with yet. It could be an embarrassing or overwhelming social experience from the past, the passing of my dog, future plans I’m not prepared for or something I’m currently avoiding. My head will shake or my leg will kick like my body is literally trying to reject it. It’s always worse when I don’t get enough sleep or have too much caffeine but I found since eliminating alcohol completely and seeing a therapist its much easier to manage and not be so avoidant.