sounds like your motor is weak. i have seen them were they just die suddenly and i have seen them slowly get weaker over time till they just give up. you got to pull the door panel and check the track for debris or damage ,check the window guides, window regulator,window roller. make sure nothing is binding in thr track and make sure every moving part is totally lubrucated. since htey are so cheap i would replace since your in there anyway. luckuly every thing you might possibly need is relativly cheap.
