Thirsty?
Are there medications you take that could have dry-mouth as a side effect? I do...but I don't notice dry mouth during the day because I routinely drink 100 oz. of water. But boy do I notice it at night! I keep water next to my bed and usually take a couple big swigs in the middle of the night.
Here's a list of medications that are known to cause dry mouth. http://wsdha.com/clientuploads/pdfs/Public%20Info/Seniors/Dr yMouthMedications.pdf
ETA: PPI meds are notorious for causing dry mouth by the way