Baby wakes up crying hysterically

Mimi • Baby boy born in April 2020 👶🏼 loss in 2021 👼🏼 rainbow baby coming in 2022 🌈

My son is 4 months old, and for the last few weeks he’s been waking up about one hour after bedtime crying hysterically. Just when I think I’ve calmed him down he starts again, and it goes on like this for 30-60 mins. After that, he sleeps perfectly for the rest of the night (wakes up to feed once or twice more with just normal grunting baby sounds).

He used to sometimes wake up from naps like this... but it’s consistently been happening lately just after he goes down for bed.

Has anyone else experienced this with their child? What did you do to help the situation? I don’t know if he’s having nightmares or separation anxiety or what? :(