Greetings,This kind of behavior can be common at age three as children learn to express themselves. The key is to be consistent and calm. When he hits or pulls hair, immediately and gently stop the action, say "no hitting" or "we don't pull hair," and redirect him to a different activity or toy. Praise him enthusiastically for positive behavior, like playing gently. Setting clear, simple boundaries and consistently reinforcing them will help him learn.

Kindly consult once for discussion

Consult with Pediatrician physically for further evaluation and treatment