From your reported symptoms... it sounds like there could a defect in the rain-sensing/automatic-wiper system in your vehicle. Perhaps a short somewhere. If true.. it should be repeatable by spraying water on your windshield where the rain sensor is located (up near where the front facing camera is) .. and hence you should be able to demonstrate it to a dealer to track down and fix.
If you are unable to repeat it on experimentation... that might mean a dealer cannot replicate it either, and therefore could not fix what they cannot confirm (intermittents really suck). At which point your next logical step is to take a video of it misbehaving..and that video should include showing that your vehicle is off, and that the automatic wiper setting on your wiper switch is off as well.
Personally, after once going through the car wash and seeing my wipers activate and fight the washer brushes until I could turn the switch off... I never leave the car wipers on auto anymore. I turn auto wiping on when it is actually raining and off when there is no rain.
