That is weird. Did you check the exhaust when you hear the noise? That’ll easily tell if your engine is on or off. If engine remains on while everything is supposed to be turned off (unlikely situation though), you should return the car to dealership ASAP, call Chrysler to open a case and ask for a buyback if possible. There are a few threads about noise while charging (not engine turning on though) and I presume yours will be something similar. Good luck.
2018 Gas Pacifica Limited, Jazz blue with Alloy interior
8 Seater, Uconnect theater HK sound, Trailer tow package.