My mouth feels odd and kinda stale?

You know how your mouth feels when you first wake up? It feels all stale and kinda dry? My mouth feels like that right now, but it started during the middle of the day so I don't know what's wrong. I was fine at the beginning of the day, but towards lunchtime my mouth started to feel weird and dry. I thought it might be because I was dehydrated, but I had been drinking water all day. What could be wrong with me? Aside from the dry mouth I feel perfectly fine. I've also been dehydrated a few times but my mouth never felt bad. I just want to make sure nothing's wrong.