On my 2018 SE I4 if I turn my car off and sit in it for a little before I get out it will make a strange sound like something is humming, sounds kinda like when you first put the key in before you begin to turn on the car to start driving. I thought it may be a pump or something moving but I don't know much about engine components. The sound lasts for like 2-3 seconds and happens about 4 min after turning my car off. Hopefully its normal.. /: