What cause that silky outlook contained by your mouth when you are tired or sleepy?

Whenever im tired or sleepy my mouth gets a unexpected silky feeling to it and i catch a weird nibble. I want to know why and how that happens and if it happen to anyone else?What cause that silky outlook contained by your mouth when you are tired or sleepy?
its nasty microbes that builds up in your mouth because of the saliva. you know, your saliva glands work extra thorny when youre tired. thats why people drool alot as ably.
Thats ******* weird. Has never happen to me.
very enormously strange!!...
silky is good though!!...