Thanks for writing to H.C.M. for your query.
I have gone through your query regarding dryness in the mouth specially when you wake up in morning. Your dryness is mainly on the sides of the tongue.
Considering your complaints it appears as you are breathing through your mouth in sleeping hours. Because in mouth brearthing as air passes in and out through mouth, or second possibility is of hyperacidity
, this also some times presents with these symptoms.
For getting relief you may take-
(b) Steam inhalation at bed time.
By this you may get relief , otherwise thorough examination of your nose and throat will be necessary by any ENT specialist