I've heard that, and personally with my hands, I feel I have control over that behavior. However I have a particular stutter behavior that happens occasionally. It's like a broken record - And I know that's a lot of stuttering, but this is severe and out of the norm for my stuttering level. I do more elongations and minor repetitions, not this violent repetition. I get stuck on a sound and I can not stop repeating it or break through it without stopping speech completely. It involves a very physical jaw movement with it. This particular behavior? I wouldn't say it's a coping mechanism but it is a behavior I feel I don't have control over when it happens. I can stop and attempt to start again and it'll still be in my 'system' so to say. It takes another word to change it sometimes.