Crying in his sleep??

Alantra🧜‍♀️ • Wife ❤ 1 son 💙 One on the way with a twin in heaven 💕

My son is 4 months adjusted age and he's been crying in his sleep lately. He'll fall asleep then whine or cry for a minute with his eyes closed then go back to relaxed.. he's been doing this for about a week or so. Anybody had this happen or know why?