My son has sleep regressions

So my son has been a great sleeper Since 2 3 months honestly no complaints. In the last 3 weeks he started have these weird changes to his sleep. He "wakes up" but is definitely still sleeping. He is like possessed to roll and sit up. He will just cry the saddest little cry or a loud scream.

It almost feels like sleep walking & night terrors. Sometimes he sits up flops over and is quiet. I will soothe him or try to nurse him but he doesn't respond until he is actually woken up or he falls back to sleep on his own.

We co sleep. And this happens 0 to 10 times at night. I will say his third tooth came in early last week so I know that is part of it.