Why is my BAS ESP light comes on & off? What Can be the problem?

if have an AWD MB and you recently replaced your rims and or tires and your rear tires are larger then your front tires (example, if your rear tires are 285 and your front, are 265) the vehicle computer thinks that the rear is passing the front and slows down your car. It will get less over time, but the best thing to do is to match the tires sizes.