This definitely sounds like night terrors. Does he nap? If not he may need to. They occur most when a child is overtired or out of routine/overstimulated. My daughter had them from about 2-7. It’s awful. Be calm, don’t make any sudden loud noises or movements. You can stir him a bit about an hour after he goes to bed, just enough to make him shift a bit, without fully waking him, this will disrupt his sleep cycle enough to hopefully avoid it. These were all things told to us that worked,