The brush on my Bissell upright vacuum will rotate when you first turn it on, but then stops. What's wrong?

I believe you need a new drive belt, or at minimum, a cleaning. Unplug your vacuum, and take off the plate on the bottom. You will have access to cleaning and checking your belt. Chances are, you can get a replacement belt at Walmart.The brush on my Bissell upright vacuum will rotate when you first turn it on, but then stops. What's wrong?
If the vacuum is only 4 months old, its still under warranty. Call the Bissell 1-800 customer support number that should be listed on a tag somewhere on the vacuum. They are usually pretty helpful.