What Causes Holding Of Saliva In Mouth?

hello doctor

I have a habit of unconsciously holding my saliva in my mouth while sleeping. This started recently since past 1 year. I feel very uncomfortable and have to get up twice or thrice at midnight to spit it out. I did not have this habit previously. SOmetimes I unconsciously swallow it or inhale it too. I feel very uncomfortable when it happens as my upper nasal passage burns when it happens. What is the solution for this? Will this affect my teeth in any way as i might be holding it for 3-4 hours at a stretch? And when i swallow it will it be harmful for my health. I brush twice a day and I am a pure vegetarian too. My oral hygiene is good except for this problem. Please advice.