The sunroof track rails are supposed to be greased regularly, it is a regularly scheduled maintenance item, and commonly overlooked. Mine had the same issue, and the mechanics broke the tabs when they lubed, it so for now I left it in the closed position.
and this wasn't done in your case. Dee8o and John Hef are both correct, it needs a specific lube, unfortunately Mercedes Be3nz sells it in huge tubs, about $50, but I have heard that Rusty's in Atlanta sells small amounts in film canisters for $5-$10

Unfortunately the sunroof on those coupes is a DIYers nightmare, don't try and fix it yourself. Will need a competent and trusted mechanic tha you have to take this on.

After it is fixed, use the pop up feature in the roof sparingly. It is the weak link in these mechanisms, and subject to failure.

And yeah, you can get better response in the Tech Help section than here.
The Diesel Disc. and Tech Help is where the real techicians and mechanics help out. Protocol is to search first. And those guys seldom come in here

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1991 560 SEC AMG, 199k <---- 300 hp 10:1 ECE euro HV ...

1995 E 420, 170k "The Red Plum" (sold)

2015 BMW 535i xdrive awd Stage 1 DINAN, 6k, <----364 hp

1967 Mercury Cougar, 49k

2013 Jaguar XF, 20k <----340 hp Supercharged, All Wheel Drive (sold)