Two things come to my mind:
1. Teething: may cause lot of drolling, hence dry mouth, hence coughing therefore he wakes upset and "kinda" coughing.
2. Dry environment: dries up his nose, hence he breathes trhough his mouth, drolling is because of that and that's why he's waking up upset because his throught is dry.
For dry mucose, try washing his nose with saline solution (or 1 lt. of boiled water -must be boiling for 15 mins- with 1 teaspoon of salt):put some drops of this solution in his nose, but he has to be facing down, so the water comes in and out of his nose (I don't know if I'm being clear here, language sometimes plays tricks on me). With this washing before his nap you make sure he has a moisture nose. Also try rubbing some Oraljel on his gums before the nap, to see if that makes the trick
If not, then we'll have to think about something else.... :wink:
