What causes Spasm and narrowing of bronchi leading to airway obstruction?

Asthma

an object can become lodged in it (as is the case in choking). or an allergic reaction called anaphylaxis can occur to a variety of substances (legal or illegal drugs, foods, dyes, plants, etc.) and...

This problem can be due to a narrowed trachea (wind pipe), thickened vocal cords, large adenoids or tonsils, decreased rib movement with breathing, and a large tongue. A condition known as...

because it can obstruct airway.

The tongue relaxes and can fall back a bit blocking the airway. That is likely the most common cause.