my little boy behaved the same, but in his case he was intollerant to a number of foods, - so maybe it could be his gut bothering him and he doesn't have ways of expressing it.. not trying to be alarmist or anything but once i addressed his food issues it calmed down a lot.. he started up again lately and i think there may be some things i am not aware he reacts to. his main intollerance is to wheat and dairy and also watermelon.
just covering all bases - or it could be that he lack of speech is frustrating him .
good luck with it.. i know it tears my hair and heart out.