2009 mini cooper s. the check engine light went on when i started it and the car wouldnt go over 20 mph. about a week ago it smelled like something was burning in the car but it didnt last long and it hasnt happened since. today when i started it, it was idileing up and down. not anything drastic but not normal at all. when i shut the car off and let it sit for a minuet and turned it back on, the light was off and it drove fine. does anyone know what this could be???