I too wake up with dry mouth, something as we age to look forward to.
I take a small amount of Biotine Dry Moth Oral Rinse. Take a small amount, rinse for 20-30 seconds, spit out. It helps!

I’ve had that problem. I believe it’s because you open your mouth when you’re asleep and it causes your mouth to be dry. I don’t necessarily recommend it, but taping my mouth with mouth tape helps somewhat. I use a full face bipap mask so mouth and nose are enclosed and air is forced through the nose.

You may want to try Xylimelts, which are a small tablet that are made to adhere to the gums. It will last most of the night and help alleviate dry mouth. It has helped me tremendously and I have told several people about it with the same problem and all have good results. They can be purchased at most drug stores and or online and come in 2 or 3 flavors. They were introduced to me by my dentist and I have now been using them for several years. They are highly effective or dry mouth. Good luck