What you have seems to be nasal allergy. It is kind of reaction to outside substance. Since its happening at night, firstly look into your bedroom for any source of dust, mold, etc which could be triggring it.
Avoiding allergens is the best solution.
Or else, for long term management you will have to switch over to nasal spray under medical supervision.
Next Steps
Try clearing house once. If persisting consult ENT specialist online or face to face
Health Tips
1. Avoid strong perfume sprays, deodorants.
2. Avoid exposure to dusts, mites or mold, use a face mask.
3. Use saline nasal wash at night.