Snoring is caused by the flapping of the soft palate when you breathe in with your mouth open. (The soft palate forms the back of the floor of the nose and the roof of the mouth.) It is made worse by being overweight, having too much alcohol, nasal congestion and sleeping on your back. It may be linked to sleep apnoea.
See Sinustis for advice on reducing nasal congestion.
Stop drinking alchol and don’t smoke.