DD used to do this. I thought with her maybe it was because she didn't like to be wrapped, as she was always struggling to get out of it, even in her sleep. After I stopped wrapping her, she slowly stopped doing the head thing. It became only when I first put her down kind of like a getting comfy thing.

I only see her doing it very rarely now, and still when I only just put her down while she's getting comfy. It certainly doesn't seem to have done her any harm

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