My 2 year old has started sleep talking and sitting up for the entire night! Last night he spent 15 hours in his bed sitting up, throwing himself about and laughing as though he is delirious. If I try to wake him up he opens his eyes (while still asleep) and pushes me away. It's very distressing to watch. Is there a deeper issue I should be worried about? Other than this he is physically well with no temp. Help!