What could cause my interior ventilation fan to not run intermittently?

I have a 2001 BMW 3-series _without_ automatic climate control, so the fan is manually operated. Starting a couple of days ago, the fan simply wouldn't turn on when I turned it on. If I leave the switch in the on-position, it will turn on every once in a while and stay on for a few minutes and then cut out again. Could this be anything more than a simple loose connection somewhere? I'll take into the shop to get it looked at, but I'll probably put this off since it isn't a major issue. Just want to make sure I'm not ignoring some more serious electrical problem. Haven't noticed anything else wrong electrically.