Adi was doing this a lot two weeks ago. Then when I finally caught him puking (he did it when i was sleeping, i could hear it but by the time i got there, he had cleaned it up himself - ick), i noticed that what came up with the food was tennis ball fabric, i tried to grab it quick, but he got it... so the next night, i was all prepared, pretending to sleep and hoped out of bed in time to get it. That cleared things up.
Anyway, maybe he got into something he shouldn't have and his body is trying to take care of itself. It will probably work itself out. I agree, if he's him happy self, keeps a good appetite and drinks, then give it some time.
good luck!