Blocked nose due to a deviated nasal septum. This is a common cause of snoring.
Nose blockage, particularly at night, causes mouth breathing. Patients wake up with a dry mouth. When the mouth is open, the mandible (jaw bone) slides backwards several millimetres, which pushes the tongue backwards and narrows the airway at a critical point - the retrolingual space. This causes energetic, turbulent air flow which vibrates any structure in the airway that can vibrate - mainly the soft palate. This causes the classic snoring sound.
A deviated nasal septum, as in this picture (see arrow), is one of the commonest causes of a blocked nose. This can be treated by a short operation called a septoplasty. This is a day case procedure under a short general anaesthetic.