If you're using the batteries that came in the box, they are frequently old and not carrying much of a charge, and tend to die quick. Could be as simple as that. Worst case, it's a bad board/loose connection to the battery inside that might be easily fixed.
I had something similar happen last night with my TV remote. It just decided not to work for a few minutes, then it was OK ever since. I changed the batteries a few days ago when it seemed like they were dead.