window broken

when i press the button to make my drivers side window go down it goes down about 2 inches and then stops if i push it again it goes down another 2 inches i have to keep doing this till it goes all the way down and the same happens when the window is going up the window will only move 2inches at a time my other window is fine any ideas what could cause this problem?
 
I get this on the Mito sometimes when the car is covered in road crud and it makes the anti-pinch sensors think there's an obstruction, clean the car and It's fine.
 
dude have you felt the anti-pinch sensors on the clio's? I had my baby finger trapped in it for about 10 seconds whilst it realised there was something actually in there! was fooking bruised for days