Too much mucous. I used to wake up choking. Started sleeping upright in an easy chair and the problems instantly stopped. Surrounded by dogs on pillows, of course. The only major problem is that the larger dog wants to look out the window and as soon as I settle in for the night, climbs up and sits on the chair top, essentially sitting on my head. Cracks husband up. Eventually dog gets bored looking out into the darkness, climbs down and we can both get some sleep.
LOL! Pooch prolly squeaks out a few vapors as well.