For the past couple of nights, and on a fairly regular basis over the past few months, I've been waking up drenched in sweat. I also get woken up at night because my mouth is completely dry - no saliva at all (this doesn't happen on the same nights as I'm waking up drenched in sweat btw). I do feel quite tired sometimes but other than that I feel fine, no illness or anything. Does this happen to anyone else, any ideas what it could be?