@Marketa he’s 16mo. Doesn’t seem to have any other signs of autism, but I will discuss with a doctor for sure Just thought maybe someone experienced the same with their babies
My son does this. I don't think he did it much in his cot but I know it's a common self-soothing behaviour to try and encourage themselves to fall asleep. I think in general it's a frustration thing where they can't verbally express how they're feeling. It is tough though and we always feel like we need to be on standby for when our son throws himself onto the floor or lines himself with something to headbutt when he's upset.
How old? Could be sign of autism maybe? Or other condition. I would go to doctor to check it