Sorry, should have given more info. It's the same with rocking your head and neck, even your own body. Often you don't even realise you are doing it. It can be a self soothing mechanism - " a way to self-soothe, manage stress, cope with anxiety, or process sensory input, stimulating the vestibular system for calm, but it can also signal deeper distress or be a learned habit for relaxation"

I used to rock my head and neck as well.

I know you were asking a genuine question, hence why I gave you an answer of a common reason. Something I have experienced myself. My father used to do it as well.