So I'm sitting at a traffic light the other day with the radio off and after about maybe 30-40 seconds this odd noise starts, goes for about 15-20 seconds and then shuts off. The best way to descibe it is like a mechanical whirring noise I guess, after a little experimentation I've noticed it goes on to do this every time I stop and idle for a little bit. I can't feel any difference while driving, nothing seems wrong that I can tell. Does anyone have any idea what this is? I've got inspection tomorrow and I'm hoping to nip this in the ass if it's something that'll fail me.