I'm used to all the weird noises my Chevy Volt makes when it's charging but when it's not plugged in it's usually completely quiet. The other night I was walking past my 2018 Hybrid Limited in the driveway and I heard a whining noise coming from under the hood and a whirring noise coming from the rear/hind driver's side quarter panel. It was not plugged in and it had been sitting there in "OFF" for at least three hours. It was fairly cold out, in the 40F range. I didn't touch the van but I did approach it with the fob in my pocket. Anything to worry about here or just another weird PHEV noise?