There must be a reason why he is behaving this way. Please try to sit with him and lovingly ask him if there is anything troubling him. Tell him that whatever it may be, he can tell you and you will not be angry with him. Similarly, dont get angry or tense when he behaves in a difficult manner. Just be calm and firm. Tell him clearly that this behaviour is not correct and that he is a good boy but something is causing bad behaviour.