allergies, acidic irritation from fruits, cumulative irritation due to dental irregularities, excessive tongue movement either during sleep or simply unaware of it while awake, dryness, etc., all potentially applicable to my situation.

Solutions are what you would expect for each of these but would require narrowing the cause. i.e. allergy tests followed by cutting out the allergen. Also a mouthguard for sleeping.

Just the knowledge that it was not dangerous made it much easier to put it out of my mind today. I am going to start cutting out certain foods for a few days at a time and see how that works.