If my bilge pump was coming on every five minutes, I wouldn't be spending time on the Internet, I would stick my head down there and see why it was coming on.
I think Lepke is on to something, your potable water is leaking (or draining) into the bilge.
If you are not hooked to city water, it will stop once your tank(s) are empty but a better plan is to look and see what is happening.
This happened to me one time, a hose came off its fitting. That shouldn't happen of course, but the previous owner or someone he hired assembled the fitting incorrectly. The potable water tank drained into the bilge and the pump was pumping it out.