Do a search on this forum for sunroof problems. I bought a 98 E320 that had a similar problem. I was preparing to replace the cable guides (which looked like a pretty simple operation) but didn't need to. All I did was pop one of them back in, as it had moved out of position. I have used the sunroof nearly every day for a few months since then with no problems.

__________________
Vienna, Virginia
1998 E320