I recently purchased a 2015 Smart ForTwo. I believe it was a Car2Go version, since it has steel wheels, leather seats, no glove compartment, rain-activated windshield wipers, touch screen console and is white with silver trim. Whenever I start it, it sounds like it is revving high for about 30 seconds and then goes back to normal. This happens whether I'm moving or not and whether I've got my foot on the gas or not. It's not a loud, annoying sound, but just noticeably higher pitch than the normal idling engine sound. Can anyone tell me what this is and if it should be a concern?