Most likely the motor shuts down as it draws too much current. Normally this is because the mechanism (window regulator) is faulty.
You have two steel cables in each door that make the window move up and down, they are lined (similar to handbrake cables), at the ends they have plastic bushes/sleeves, they often break....
Time for a new window regulator me thinks.... that should solve your issue.
They are not too expensive, ballpark 30£