I think at night you're breathing through your mouth, that will dry it out pretty bad.
Maybe try some sugar free gum when you wake up, or water.

I found water and lemon or even coke can help clear phlegm stuck in throat.
I think the acid breaks it down. I get a lot of it on the left side, I can feel it there but it's too hard to get up so I try to ignore it.
I have a sinus issue too which is just adding to it I think.