what does the exclamation point in a triangle above the speedometer mean?

Mercedes has usually used the exclamation point icon for the traction control system. It should explain this in your manual, though. I haven't driven the ML350 yet, but you could ask the folks on the Mercedes forums at http://www.mercedesforum.com/ for help. Good luck!

if its on all the time then you turned off your Trancion Control Stability...its recommended that you leave it on as it prevents your vechile from excessive wheel slip and instablilty on wet or icey roads...thus the naming Tranction Control Stability

Does it slow.down when the yello triangle comes on?

Yes

Should that not be fixed?

And do you mean traction?

it didn’t slow down when I reached 60 .....and my tires have the right amount of air? Where do I find the traction that’s on?

For some unknown reason it stopped coming on