Oh i know what you mean, my ds used to do the same thing!! everytime i put him into his cot when he was little he would look over my shoulder and smile!. I have to say he is 4 now and things are havent stopped either. to many things to go into detail about. My mum also went to have a reading done and they picked up on my ds.
I used to think when he was doing this that maybe it was someone in my family that had passed.