Your wipers start every time you use Reverse or just when your in a garage and use Reverse?????
Dark-ish garage (parked nose in, but happens day or night), ignition ON, reverse engaged --> auto-wipe initiates a sweep.
EVERY freaking time.
P.S.: Garage has a roof, if someone is wondering, with no moisture or condensation on the windshield. Just the shadows to spook the rain sensor.