Thick yellow saliva in morning when wake up; 54 year old woman?

Possibly Mucus: If your saliva is thick, there is mucus within, possibly you're a mouth breather with sinus congestion. You may want to consider seeing an otolaryngologist (ear, nose, throat physician), if your sinus has been a problem. You could also try nasal saline rinse (neti pot) prior to going to bed to clean and rinse your sinus and see if this helps.