Baby sleep, scream, sleep

Donna • First time mom of a beautiful baby boy married to a handsome mechanic just turned 21!
OK ladies my son has been an amazing sleeper since we figured out his acid reflux and everything but recently he has been sitting straight up and screaming like his in pain or scared but before we can get to his room he's already laying back down and asleep. I don't know what's going on or what to do if there is anything to do. He's still sleeping really good but just wakes up long enough to cry. Do I really need to do anything because he is sleeping or what