Your salivary glands produce two to six glasses of saliva per day, about 0.5-1.5 liters. You still haven't choked on it, because you constantly swallow it reflexively.
But at night it is quite possible because people do not know how to swallow in their sleep. And so that you don't choke, the body reduces the amount of saliva produced. Therefore, when you wake up in the morning, you usually feel a dry mouth. Saliva is also a natural pain reliever. One of the most powerful and effective pain relievers known to science, opiorphin, is produced in saliva. Also, introverts have more saliva than extroverts.