The main cause of snoring is relaxed muscle tension in the back of the throat, which can lead to a narrowing of the airways and the vibrations of relaxed muscle tissue. Another cause of snoring is congestion of the nasal passages which can limit or block airflow through the nose. This can be due to colds, allergies or a blocked nose, which forces you to breathe through your mouth and can lead to snoring. Lifestyle factors such as drinking alcohol, smoking, and being overweight can all make you more likely to snore. You can find out more detailed information about the causes of snoring and how to prevent it here.