Driver window not always working

What's the reason my driver's side window sometimes won't roll up. It works fine most of the time and every once and a while it will only go up a little then stop. How should I diagnose my problem. Before I buy any parts.

 

Lack of lubrication can definitely cause that. I personally would have to remove door card(panel) and observe that the nylon pivot points are moving smoothly in the tracks as you raise/lower.

 

I believe there's a sort of safety overload built into the motor. Pop the door card like Bubba said. Clean the tracks. Get an old tooth brush and shop rags for cleaning the tracks. Re-lube the tracks. Wipe down the inside of the rubber guide the window slides in and make sure there is no binding in the rubber at any point of up or down travel. Sometimes the rubber will get chewed up and start to drag and cause binding on up or down causing the motor to stop. I'd check all this before buying a new motor. They ain't cheap.
Make sure at the front guide that the window is sandwiched between the rubber window run on both sides. At some point mine was between the metal guide and rubber at one point that I noticed. And as it goes up sometimes would cause drag.

 

See that scissor-like assembly @BubbaW posted?

Note the bolt holes. Sometimes the bolts come loose, and will result in erratic behavior out of that scissor system, and can also result in the assembly getting bent up.

 

It's still bad even with lubing it up. It just took me 10 minutes to get it all the way back up.

 

I know that tacos and runners have an internal circuit breaker, that will trip when hot. I just replaced the motor on my friend’s taco, for this exact reason. Window would work ok, then nothing. Wait a bit then it would work again. Removed the tracks and refurbished a bit, new motor. Everything is working now

 

Did you inspect the rubber window run? The rubber has a spot in the metal track. If it is torn, which you can't sometimes see if it's in place it'll cause binding on the way up. Gimme a sec I'll give ya an example of what I mean

 

So this is what could be on the inside of the track causing resistance this maybe causing the internal breaker to stop the motor on the way up.

 

I will have another look tomorrow.