Your not the only one with this problem, my '95 GLX does the same thing except when i open it in slide mode it takes forever to close. Anyway the problem may be the pin that slides on the track its a little silver piece that you can only partially see. In order to determine if this is actually the problem you have to take the glass out of the roof via 4 torx bit screws at the four corners of the glass. The pin on my GLX is broke on the drivers side, but check both.
P.S. be careful when taking the glass out make sure the tracks are even otherwise it wont go back in straight...and thats a bitch