L.H.
any diet changes? what does he eat at night? I would look there first...
then I would offer him something to do when he wakes up
like keep a cup of water by the bed & tell him to take a few sips, take a few deep breaths, get his blankie or whatever and then maybe sing a song and go back to sleep
sounds silly, but maybe having something to 'do' might help
focus him and get him back to sleep
make it fun & silly
and you can role play the things you decide he should do
and while you role play you can take turns being him-
little ones love when you are 'them' so you can be him and get in his bed and play-act crying, really ham it up and be silly' and then go through the motinos/steps of what it is that he should do when this happens to him- ie: take a sip of water, get his blankie, climb back under the covers with his bunny
and sing 'twinkle twinkel' or something- whatever you think would work
good luck :-)