Many reasons can cause this. The problem may be in your room it self 1. AC - get your filters cleaned. May be allergic to fungus from AC. Use a humidifier. Sometimes excessive cold air directly on the nose can cause nose block. 2. Dust, dust mite on the bed linen, screens etc. You may be allergic to it. Vaccum clean your room. Wash the linen in hot water every week. Can use a short term steroid nasal spray. 3. You may be having a deviated nasal septum with enlarged turbinates.. but that causing block only at night is unlikely. 4. You may be having laryngopharyngeal reflux. Sometimes acid reflux at night can happen once you lay down and may cause airway inflammation. Which may result in breathlessness at night. 5. Do you smoke or consume alcohol at night.. both of which may worsen above said problems and can cause breathlessness at night

Is it when you use AC? If so try using a humidifier it will be helpful. If it happens irrespective of AC then get it examined.. thanks

It could be acute nasal obstruction due to allergic conditions or it might be deviated nasal septum with add on allergic rhinitis . It can also be due to hypertrophied turbinates You can use sinarest nasal drops for 5 days to get relieved of acute obstruction However please do consult if problem persists Dont use sinarest nasal drops on a regular basis

Could be deviated nasal septum Should ho and get it examined properly

There could be many reasons First of all since how many days ? You need to visit for physical examination