Constant, conscious swallowing of saliva at night

It's happened to me maybe three times in my adult life. Now, it's probably once a month. It all starts when I turn the lights off to go to sleep, and suddenly I become conscious that I have saliva in my mouth and that I have to swallow it, and If I don't do it manually, the saliva just accumulates in my mouth. When I enter this horrible circle, I can't sleep, my stomach fills with air, and I wake up with a sore throat. Has it happened to you? Is this a symptom of anxiety or other thing? How did you resolve this? Sometimes I feel like it's a panic attack. It's exasperating.