I got your e-mail, and unfortunately I have no direct experience with the tilting type mechanisms. I can tell you you have to remove the interior cover of the sunroof to get at the mechanisms and see what is hanging your roof panel up.
If you can close the roof, then the it is likely that the problem lies with the force required to go any further in the opening direction is causes the clutch mechanism on the motor to slip. There are rails and other surfaces that need occasional lubrication, and there is the chance something has come loose and is jamming the mechanism. And there are procedures for adjusting the clutch. I would make sure the mechanism is clear of obstacles and well lubed before tightening the clutch, as you may damage the drive gears if the clutch does not slip and the roof is jammed.
If you do a search on sunroof repair or the like, you will get a number of hits with good information. This may be more of a seasonal topic as in the summer there were many posts on the subject.
Good Luck, and I hope this helps you on the way to getting some expert help along the way. Jim
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)