Self soothing or teething?

My son sleeps in the love to dream 50/50 swaddle with wings on it. He keeps falling asleep with his hand on his mouth and sometimes tries to suck it but can’t. He also tries putting it in his mouth when sleeping but he startles him self and wakes up. I tried to leave his hand out well sleeping and he hates it. Is he teething in his sleep or trying to soothe him self?