Hi there, My son is also 4 and hits me sometimes but mostly he hits others when they try to take something from him. I believe also that my son is not mentally stimulated enough and that nurseries and pre-schools don't really have the staff or skills to help teach some of the older children before they start school. I normally ignore my sons behaviour for as long as possible but if he doesn't stop i warn him that i'll put him in his bedroom if that doesn't work i simply take him to his bedroom and hold the door shut for 4 minutes. Usually hes crying and will say sorry with a little prompting. Good luck and i hope i could help a little.