baby waking up screaming/crying

my son is 5 months old. he has NEVER done this before until today, and he just did it for the third time.

he doesn’t even cry like this when he’s awake. but he’s just suddenly waking up crying super loud. even once he’s awake and sees me and i’m talking to him or holding him, he’ll pause and keep crying. he seems so distressed.

no problems during the day while awake..no problems once i do get him to calm down. and again he hardly cries but when he does it’s very calm and low and it’s easy to console him. this one is high pitched, panicked and takes minutes to calm him down. that’s why i’m so alarmed..

could it really just be a bad dream? i have no clue what’s happening