Hi Steve, this does sound scary, but you are correct in assuming it is likely your dog dreaming. They sometimes seem to be running marathons or chasing birds in their dreams. They can vocalize and move their body quite a bit. If your dog is happy and healthy when he wakes and behaves normally at all other times, I would not worry too much. If you are still concerned, please video this and show your veterinarian or even entertain your friends on Youtube! Wishing you and your dreamer the very best.