Baby sitting up In sleep? Is it normal?

So, the weirdest thing happened last night. It actually creeped me out. I put my 8 monther to sleep at 8pm, around 11 me and hubby went to the room to sleep. And suddenly my baby just sat In his sleep, with his eyes closed and rested his head on the side bar of the bed. He slept like this for about 1 minute, me and hubby just watched him. After a minute he moved and fell back down, and literally It was as If nothing happened. He was sound asleep.. Anyone gone through this? Is It normal? I'm getting the creeps.