Hippy had a habit of doing this too - he'd grab reins, lead ropes, sleeves or whatever was in close proximity lol!
All I can say is that he seemed to do it when he was anxious, like a comfort blanket :) I'm not sure how I'd go about stopping it as our loan pony no longer does it very often, but maybe make sure he isn't anxious and check his bit fits right?
Does he do it all the time? Just when you are doing something particular? It would help to know a little more. My guess just by reading he is playing with his bit is he must be bored. Posted via Mobile Device