Benz84 - I recently had the exact same problem with my sunroof on an 86 190E2.3 16V and i am almost sure what yours is. First before i can really be sure you have to take off the cloth cover that is the bottom of the sunroof on the inside of the car. This can simply be done by deforming it a little bit so it can slide out. Once you have done this you can see the roof and the cable is exposed. Now there should be a small gold clip that grabs the cable where it connects to the piece of the roof that slides in and out. On my car this piece became bent over time and would no longer engage the cable to the motor so the motor would run and the cable would not go down. But if you disconnect the cable from the clip and you push it gently back toward the trunk and push the button to engage the motor the cable should get sucked back by the motor. If this is the case then you most likely need a new clip because the old one is deformed or you just need to make sure that the clip has a tight grip on the cable. If either of you have any more questions i am glad to help.
1986 Euro Black Metallic 190E 2.3 16V