Other Why does he hit his head?


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I have a nephew, about 10 months old. I was holding him in my arms and he started hitting his head on my face, and then was hitting his head with his hand.
About a month back, my mother told me he was hitting his head on the wall.
His mother was exposed to my narcissistic father when she was pregnant with him, and I also notice my father being threatening towards him, often trying to scare him by raising his hand as if to hit him.
Could he be hitting his head due to stress or something related?