I just received my car a few days ago so I could just be worrying about nothing. Today when getting out of the car and having it turn off, I noticed a loud humming coming from under the car, it sounded like a motor or something. The humming faded slowly over about 2 minutes until you couldn't hear it anymore. This wasn't the charging or anything like that, it started before I plugged the car in. Should I worry about something like that? Temperature is 25F outside if that makes a difference.