I feel your pain!
I have read up on sleeping and in particular, sleep cycles. From what I have learned is that every 90 minutes your body goes into another sleep phase/cycle and with babies its every 45 minutes. It sounds like this little one is having difficulty going into his next sleep cycle. Is he sleeping in a playpen? If so I would go and lay him back down. No talking, no eye contact, dark room with a white noise machine/loud fan and leave him for the remainder of nap time.
At this age he should still be napping 2 hours each afternoon IMO.
Good luck!!