I'm gonna' say take off the door panel.
It could be a number of things. The window could be off track, or there could be something stuck in the track or getting in the way, or possible the motor is giving out.
Take the panel off and plug the window switch back in and watch how the window rises and falls and see if something looks wrong. If you can't really tell what may be right and wrong then take off the passenger side and see how that one operates.
I know it's not a quick fix, but this may take some troubleshooting to figure out. I personally haven't heard of any window issues like that.
What year is your car again?