Does anyone else's LO thrash their head from side to side - it looks like DS is whipping his head back and forth to say 'no' - to help self soothe? He doesn't do it all the time, but I have seen it come and go and it is really weird to me. I would think that his neck and/or head would hurt afterward. It makes me think of a headbanger! Is this ok? I have never heard of it before.