Well, despite the E320 being a very expensive car...things DO happen. New cars usually have a breaking in period for about 5,000 miles after they are purchased. I haven't heard of many things going wrong with Mercedes-Benz cars, but hey, they are still produced by human beings, and therefore subject to failure. A friend of our family had an '88 300E which had to have the computer replaced after a couple of months, but the repair was covered under warranty.
My dad's '84 Volvo 244DL had to have a new starter put in it within a week after he'd bought it new because it was hard to start. Volvo replaced the starter without any problem, and the car currently has over 250,000 miles on it. Frankly, I'm amazed it's still running. My grandmother's '87 Volvo 744GLE had to have a new transmission put in after only two years being on the road, but again, Volvo replaced the tranny free of charge as it was under warranty.
Superfly, we won't go into what sorts of repairs had to be repeatedly carried out on my grandmother's 1980 Seville, or my parents' 1982 Cadillac. Most of the problems were somehow NOT covered under warranty, and the service department personnel were belligerent and unhelpful. Sure, much has changed since the '80s, but human beings tend to operate based on the past.
FYI, cars are not an investment, but rather a liability. They continually depreciate...unless you have a '48 Tucker Torpedo or some other rare collectible. BTW, what do you think of THAT car, Superfly?