As far as I'm aware you're mouth doesnt produce saliva when you're sleeping. So if you get up in the middle of the night it should be dry. As long as you dont wake yourself up too much or move your tongue around you should be able to get into a trance without saliva forming. If you've just woken up it will also solve the problem of your mind being too awake.
I get the breathing problem sometimes too. In my case its from thinking about controling my breath. I can be aware of my breathing in a trance without it messing it up but if I accidently think about the fact I'm capable of consciously controlling it then it's like I get partial control again which is hard to relinquish quickly.
To echo the others, the best thing to do is keep your attention as far away from your breathing as possible. So you need something to concentrate on. Try as many techniques as you can find and use the one that you find keeps your attention best.
I get the breathing problem sometimes too. In my case its from thinking about controling my breath. I can be aware of my breathing in a trance without it messing it up but if I accidently think about the fact I'm capable of consciously controlling it then it's like I get partial control again which is hard to relinquish quickly.
To echo the others, the best thing to do is keep your attention as far away from your breathing as possible. So you need something to concentrate on. Try as many techniques as you can find and use the one that you find keeps your attention best.