My daughter...when she's gets upset...she will slap herself on her arms and hands.
As long as there are no other unusual behaviors to suggestion something else, he's probably just trying to find ways to express all the emotions bottled up inside.
Ask him to use his words. Tell Mama what you need. Then say..."I need..." and try to get him to fill in the blanks. I don't know how old he is but if he can talk, maybe he's just frustrated with not being able to express his feelings.