1. Your nose naturally alternates sides every few hours (the nasal cycle). When you lie down, gravity and blood flow make this cycle more noticeable so congestion often feels worse at night even if nothing “new” is wrong. 2. Lying flat increases blood flow to nasal tissues. This causes the turbinates (normal structures in the nose) to swell, narrowing airflow and creating that “blocked” feeling. 3. Dry indoor air dries out nasal lining, then your nose overcompensates. Overheated or low-humidity