general problems of the 1999 Mercedes Benz E320

My car skidded of the road after I tried to brake in order to slow down because two right wheels of the car were in a puddle. I completely lost control of the car, and did not understand what was happening. I was on a ramp approaching highway 101, and I was not speeding. It was a really scary moment. I took the car to the mercedes dealership, and their conclusion was that there is nothing wrong with the car, which is hard to believe.