crying in sleep

For the past few nights my baby starts randomly crying at night, he is not ready to get up or anything and when I look at him through the camera I can see that his head is down which when he wakes up he puts his head up right away. I don't know what to do, should I hold him or let him cry? I have done both he cries for like 20 min and sleeps and when I go to get him he stays awake but isn't hungry or anything, I just don't know what is best Thanks! FTM here so idk 🤷