I just barely went through this issue with my 1999 C280. I would like to take a second to completely explain my experience from beginning (problem) to end (solution).
Initially, my wiper was occasionally sticking. At the time I was thinking that maybe the type of wiper that I bought from auto zone wasn't compatible or that maybe the windshield glass treatment that I was using was causing the rubber of the wiper not to slide as it normally would. Eventually the problem got worse and would completely stall. My wiper motor would continue to make noise as it attempted to force the wiper down and would eventually shut itself off. I would later have to get out of my car and reengage my wiper switch to the on and then off mode as I guided the blade back to its starting point so that it was no longer frozen in the middle of my windshield. At this point I decided that it was time to take a deeper look at what was going on with my wiper system. After reading about a million different forum posts I was able to find and create a very good path of diagnosing and fixing the problem.
***I will reference the following two links throughout. Don't worry about viewing yet. Just follow my path.
link A- http://202tech.mkosonen.com/howto/wiper.html
link B- http://members.lycos.nl/mbenz/windshield_wiper.htm
(link B actually explains another procedure but it has great pictures and directions of removing the MB wiper system as well as how to put it all back together so that it works)
First, I just want to familiarize everyone with the main parts that make up the MB wiper system. There are five main parts to the MB single wiper system.
1) First we start with the wiper arm, commonly called the windshield wiper, that everyone is familiar with.
2) Second, we move down to the mechanism that holds the wiper arm, which is technically called the Windshield Wiper Transmission but referred to as the wiper mechanism throughout the links. Strangely however, link B refers to the entire wiper system as the wiper mechanism and then later calls just the transmission the wiper system.....so keep in mind when reading (Viewable at the bottom center of your windshield and about the size of a small football.)
3) Next, we move down to the wiper linkage, which is referred to as the offset plate in link B. The wiper linkage or "offset plate" simply connects the wiper motor (#4 below) to the wiper transmission (take note, you cannot yet see this item without removal of the entire wiper system).
4) Then, we have the wiper motor, as mentioned above. The wiper motor drives the wiper linkage or "offset plate", which activates the wiper transmission, which moves the winshield wiper back and forth in order to remove snow or rain
5) Finally, we have the mounting bracket that holds the above parts 2, 3, and 4 all together and to your car.
1. It is very possible that the solution to your problem is just a quick five minute lube job of the wiper transmission. Take a look at link A for great directions and pictures of how to do this. If this is your problem then you are done.
If not....as was my case continue ahead
2. Your next problem could also have a fairly quick solution. Part # 3 above, the wiper linkage or "offset plate" connects to the wiper transmission and wiper motor by a pressed fit, secured by a nut. It is a very common occurrence that the nuts that hold the wiper linkage to the wiper motor and transmission eventually loosen and cause the linkage to slip out of correct positioning. If this happens it will cause your wiper blade to hesitate or stall because the linkage or "offset plate" has to be connected to the motor and transmission very tightly and in a marginally specific timing or position in reference to the motor and to the transmission. Take a look at link B to get an idea of how to remove the wiper system and reset the positioning of the linkage or "offset plate" in reference to the wiper transmission or "wiper mechanism" and wiper motor. But first before you do so you are going to want to pull the wiper transmission off of the wiper mounting bracket and inspect and lube the graphite gear found on the opposite side of what you lubed up in step #1. It is rare for this gear to be chewed up but if it is then you will be replacing the wiper transmission, which I have heard can cost around $ 700.00 for the OEM part and still possibly the linkage and motor
***Back to reseting and retighting the linkage "offset plate". remember that the surface of the linkage is a beveled pressed fit, so as long as the surfaces of the linkage aren't too chewed up you should be able to drive that nut on hard enough to achieve the necessary pressed fit. However, if the linkage is too chewed up from slipping for too long, you may have to buy a new linkage. The best deal that I found on this part was at http://https//www.autopartsway.com/secure/cart.cfm I think it was appx. $ 45.00 or $ 50.00