I've had this happen to me but only for a few seconds, usually it happens at 2:00AM and it makes me wake up with a start!
It could be a couple of things, it could be a leaking valve that is letting a slight amount of water pass. Check to see if your toilet is not quite shut off, or the bathroom tap is leaking slightly.
It could also be that your system is just pressurizing again, but then it would only run for a few seconds, not minutes. You might want to see if your black or grey tanks are filling up, the water pump may be filling those up.
I installed a small pressure vessel and it took care of that plus it allows me to run the tap for a short period of time before the pump kicks on.
Let us know what you find.