See sticky thread "W220/C215 instrument cluster recall"...
http://www.peachparts.com/shopforum/showthread.php?t=165879
MB should expand this campaign to include additional models, like the W210 (yours) and the W208 (mine).
The issue is the same. The conductor leads on the mylar ribbon cable attached to the displays deteriorate over time, causing loss of pixels on the LCD displays...for most, this relates to the temp display and the shift indicator.
There was a post at one time by an electronics whiz who was able to painstakingly fix his own using a conductor pen and strong magnification...seems like a daunting task to me though.