Jasper used to do that a bit, I'd come running and then look at him and he was fast asleep... I think they must have nightmares!
Also, around that age Jasper found this AWFUL scream, it scared me so badly the first few times, he scream so hard his voice would break and no noise would come out! I would shatter my heart (and eardrums)!!! He survived (and so did I) in case she adds that to her voices soon.