My is one and half month oldhe keeps moving his

Patient: My is one and half month old.he keeps moving his had taken him to an opthalmologist and she said all is good.his vision and eye all good.she also said the number that she got is too small to even give glasses amd its not nystagmus as incase of nystagmus the number be’s very high.what can be the reason behind it.will it go on its own.please help.