Wakes up crying!

Adrienne

So recently my 13 month old has woken up in the middle of the night a few times now crying uncontrollably. He's not really a cryer so it's really weird and it takes me 15 minutes to an hour to get him back down by rocking him, holding him tight and putting on lullabies. I don't know what's wrong. No temp, no teeth that I can see that look bothersome. I feel awful for him. Anyone have any insight???