1. Make sure the belt is in contact with the shaft. 2. Remove the roller and clean the brushes AND the area that seats into the vacuum. If there is too much hair, string, etc. the brush may not roll. chances are the belt is probably not making contact. If it was you would smell rubber burning if the brush wasn't turning.
Check to make sure the belt has been "scooped up" by the hook in the head. When you turn the knob on the head to remove it, it's supposed to "scoop" up the belt and pull it away from the shaft. If you don't have the belt on the hook when you place the head back on that means the belt isn't going around the shaft. You can just use your fingers to place it in position so the hook will grab it and then place it back on the body, rotate the know and it should be in contact with the shaft. The only other problem could be that the belt is broken and needs to be replaced.
Check the brush roll to be sure it's spinning free too much drag can cause that to get hotter but usually it would break the belt. That spindle will get hot from the friction created by turning the belt and from the motor's heat. They'll just get hot, any brand that spindle will be hot after running it. It's just how it is.
