Five beeps? a countdown to explosion?
No, but probably a burnt out light. They light up at start just to check they're working, then complain if they aren't. Or one that isn't going on for some other reason. IIRC the circuit includes sensors in the seats, so do a quick check of those. Replacing a bulb in the dash can be a real project, although probably easier on older vans.
Did you notice any blinking on the airbag light before it went permanently dark and the beeping started? On some cars where I tore out the airbags the lights would blink incessantly as the primary warning system, then when I yanked them I'd get beeps, the backup system. So it's possible there's a real fault in the airbag system that is more than just the light; but if it's burnt you'll have to replace it to get rid of the beeping in any case I suspect.