Sleep Apnea occurs when your tongue and soft tissue at the back of your mouth block your airway when you sleep. This blockage is what causes snoring. If you are over-weight, this too can contribute to your risk.
Take this Tongue Test
Grab a flashlight and go stand in front of your mirror. Stick your tongue out all the way, shine the flashlight into your mouth. If your tongue blocks your view of your uvula (the little hangy-down thing at the opening of your throat) you have a fat tongue. You may also be suffering from Sleep Apnea.