Kenmore Elegance Vacuum, Model 116.30750400C / Serial # M41901532?

I have a Kenmore Elegance Vacuum with Dirt Sensor, Model # 116.30750400C, Serial number M41901532. When vacuuming the carpet the power head will work for 3-6 mins then automatically shut off, power is still there and lights work but the power head motor turns off and the suction stops. I will turn it off and on, check the outlet, flick the on off buttons...nothing. I will turn it off for a couple minutes and it turns back on and runs like normal. I've check the bags, filters, cleaned the hoses, intake at the power head and to the wand. What's up with this? It only does this when I use the power head? It's driving me insane!