If the structures in your nose are so large they completely block the throat, air cannot pass through to your lungs. This is called apnea. When you are sleeping and your lungs are not getting enough air your brain tells you to wake up enough that the muscles can tighten and you can get air through the blocked passages. This may take place several times during your sleep cycle even though you may not realize it is happening.
Some of the symptoms of possible sleep apnea are: feeling drowsy during the day, waking up tired even after a full night of sleep, waking up with a headache, crankiness, or short temper and having problems with concentration and memory. When you have sleep apnea you are at risk for high blood pressure, heart attack, and stroke. If your doctor suspects that you have sleep apnea he will probably prescribe a sleep study in a sleep clinic.
One thing you can do on your own to help with apnea and snoring is to sleep on your side, which may keep air passages from being blocked. Losing weight can help with snoring and apnea by taking some extra weight off your neck muscles and lungs, making breathing easier. Your doctor may also suggest that you have a Septoplasty or a UPPP (uvulopalatopharyngoplasty) to help aid in opening the passages to your throat.
When you breath, air passes through several structures on the way to your lungs. These include your soft palate, uvula, tonsils and your tongue. While you are awake, the muscles around each of these are tight and hold the structures in place. When you sleep your muscles relax and normally enough air passes through. When these structures are too large or your muscles relax too much your air passages may be partially blocked. As air is trying to get through your nose or mouth the air is moved around causing vibrations, which cause the sounds of snoring. This can be made worse if you have a deviated septum (the bone and cartilage dividing you nose is crooked).