My son's 97 Grand Prix GT 2 door was doing the same thing, so I bought a new power window regulator on ebay for $50 and installed it tonight. without the window in, the track goes up and down quickly. When I put the glass in, the window starts going slow and stopping again. It must be the tracks, or the mount to th regulator. It seems like there is too much play in the window and it gets cocked one way. I ran out of time tonight and will let you know what it is once I fix it.