* Make sure he has a couple really hard things to chew on. Bunnies teeth never stop growing and they have to chew to keep shortening them. The paper towel rolls aren't tough enough for that. A couple nice chunks of hard wood are great, and help them wear off excess energy and those too long teeth.
*Could be attention-seeking or acute cage boredom. Could be irritation with noise when he'd prefer to be sleeping. Could be desirous of a desirable partner (for all of about 1O seconds ). Could be unhappy about some aspect of his cage. Could be too little daytime/daylight activity. Could be...