Could be a wire broken.

Try the black -ground wire inside the tube that goes to the driver side door. It is likely broken but not seperated--two ends are still rubbing each other so the problem appears intermittent.

If that is the case, it will get worse not better. One day one of the windows will stop going up or down completely.

It happend to mine on a rainy day and one of the darn windows refused to go up....

Hope my experience helps and good luck.