mY 2004 DID THIS ON THE FREEWAY, after driving for about 30 minutes, and started up again after about 30 minutes. This behavior was repeated twice the next day, so I
Took it in to the dealer to have the computer check the codes, nothing.

They ran it a while and it died, and when they went to check out the codes discovered the module was hot to the touch( not supposed to be) so they replaced the processor. to the tune of 2.5 k $. The part was 1700$, and they had to install it and reprogram all the functions it controlled.

Both the mechanic and others I have talked to say this is a comon problem for this 3.2 litre DBenz engine, at 100k miles. mine had 101 k at the time.

That was a month ago, and the problem has not recurred...but I am keeping my AAA card handy.
hope this helps, email me if you need more info and I will find the paperwork.
Chuck