OK, this 2000 ML320 was purchased 1 month ago from a used car dealer with 60k miles. Here is the problem:
At certain times, the ABS/ETS/ESP lights come on simultaneously. It happens in cold weather (less than 25F) or when I was in the snow and ice recently having a little fun making the car slip and slide a little. When it is really cold, I could sometimes drive very, very easy after starting the car and the lights would stay off. Once I drove a couple miles, I could resume normal driving and the lights will stay off.
If I drive with normal acceleration after a cold start, they would come on within the first minute and stay on until restarting the engine.

The car dealer replaced the brake light switch for me, saying it was a very common problem....did not fix it.

I dropped the car off at a garage specializing in German cars to see if they can diagnose. They have a good reputation and told me if they don't feel 100% they would recommend taking to MB Dealer.

Can anyone help me out here?

Thanks,
Scottie