Swimming to Sleep?

Collin has been a big boy the last two nights by putting himself to sleep without needing our help. He looks funny doing it though. Instead of laying there in his crib cooing and then falling asleep, he does what looks like the breast stroke (on his back) while moving his head from side to side. He will do this a few times, rest and do it again. He "talks" while doing this too. Weird as it may look, he usually falls asleep within 15 minutes and has stayed asleep for at least 2 hours before stirring again.

He has been moving his head from side to side rapidly at night before when we put him in his crib after we swaddled him. I thought the head movements were him trying to get out of the swaddle and letting us know that he did not need that anymore. He still moves his head but does not need to be swaddled to fall asleep.

I am working from home tomorrow and looking forward to spending the day with him. Mimi is coming over to help me so I can work most of the day.