I've seen it before, but don't know why some kids do it and others don't. My husband can remember his younger brother rocking every night in order to settle to sleep. He grew out of it (we think! Hehe). Ask your doctor about it on your next visit and see if they know what might help your boy to grow out of it faster.

All my kids have done this. It's just a phase they're going through. Nothing to worry about.

both my boys done the same i have no explaination for it but they do grow out of it, my youngest is only 2 so he has just started it and the oldest is 11 and he no longer does it, i think it was a comfort thing for him, i can't say for your son but i know with mine he done it whateva mood he was in too but his body langage told me that he done it for comfort just like some kids have a doll or blanket