power windows not so powerful

I just picked up a 94 Astro. The power windows do not work so well. The passenger side sometimes goes up & down just fine, sometimes goes a couple inches then stops. The driver side goes up or down only about an inch or two at a time, and I have to wait about 4 or 5 minutes before I can get it to move again. I tried jumping the switch and that did not make a difference. I have not tried to apply 12 volts directly to the motor yet. I was wondering if there is a circuit breaker or a relay that heats up and resets or if there is a common problem with these. Please help. This really sucks when it starts raining!