I think my baby boy had bad dreams! He is 5 1/2 months old and he has pretty much slept through the…

I think my baby boy had bad dreams! He is 5 1/2 months old and he has pretty much slept through the night since birth, but just recently he will be in a deep sleep and just wake up whining and if I don't hurry and pick him up and rock him he goes into a full out cry until he falls back asleep... I am a FTM so anybody experience this before and has any suggestions as to what to do to help my baby boy, I feel so bad!