Living here in the Midwest, cold has set in for the long haul. I have noticed my bug makes a whirring/humming sound when I first turn it on in the morning. It continues for a few minutes until it warms up. It only does it when it's been sitting all night in the cold. Is this a common occurence or should I have it looked at? Both my bug and I are having a hard time adjusting to the cold weather!