Yes one nostril is usually open, but not always.   So tape my mouth shut?  Leave the corners open?  Can I get some more detail without buying the book?

They sure do seem like a virus that gets triggered. But I don't think anybody has found a virus, so I'm keeping an open mind. In any case, breathing through my mouth at night seems to trigger them. 

 yeah, the tape just holds your lips together just enough to convince or remind your body to breathe through your nose.