Recently (in the last year or so) I've been waking up occasionally during the night to a severe choking sensation, and I can taste vomit or bile in my throat and mouth, and it doesn't go away until after at least half an hour of strong coughing, and even then the taste stays with me. What could this be?
This could be a sign of reflux. Reflux is often worse at night when we lie down. You should discuss this with your doctor. In the meantime you may want to try some preventative measures to help keep you from waking up with this. You may also want to consider keeping a food log to see if there is any correlation with what you ate and when and which nights you wake up.