Update: I took the car to the dealer. It is not the battery. The battery is fine. It is an EIS issue. I'll post another update when I know more. I'll probably replace the battery also, just because it is old and with this cold weather (it's about 7 F right now) the chances of battery failure do go up.

The car stopped in the middle of the road while I was driving to the dealer, so I had to get towed the 50 miles (300$ tow bill), and when I got to the dealer the idiot working at service told the tow truck driver to leave the car behind the building. Fortunately, when I walked with a tech back to the car it started. (Unfortunately after I'd already been towed there) He drove it into the garage and did some tests. He had to turn the car off, and then he couldn't turn it back on.

They put a new battery in the car just to test, and the key still wouldn't turn in the ignition. They can't hook up their computer to the car to check for any error codes or software versions until they can turn the key in the ignition.

 

Update: Sadly, the entire EIS and key have to be replaced. That's going to run me 950$

 

Eis (electronic ignition switch) needs coding, and special order part...ouch expensive!

-mar-

 

I had the same problem with a 96 and the dealer was less than helpful.
Next car will be a Lexus.....I've had enough grief with Mercedes and the dealer.

 

Update: They replaced the EIS and the battery, and they told me the car was fixed. I went to the dealer to pick it up, and it wouldn't start. -_- WTH is wrong with this car???