The COMAND infotainment/navigation LCD (and the in-cluster displays on early cars) commonly fade, distort or develop dead pixels, aggravated by heat. It is treated as a low-stakes, well-documented fix: replace the unit with an inexpensive used OEM screen from eBay or upgrade to a modern aftermarket head unit with CarPlay/Android Auto, retaining steering-wheel controls.
COMAND LCD screen fade and pixelation
Mercedes-Benz SL (R230) · cosmetic