It sounds like it might be related to the dry mouth. It doesn't sound serious. If it is bothering you, you might want to place some type of lubricate on your lips before you go to sleep.
Just a detail I forget, I only see these on my upper and lower lip in the morning and it varies from not being present to slightly more severe, but they always look the same, though I do seem to have whiteness on the back of my tounge usually.
And it's only right when I wake up, when I lick them off usually, they don't re-appear again until the next morning.
I used the word "Usually", sorry about that, I just want to put emphasis on the fact that I -never- see them re appear later on once I have licked them off after waking up.