for a shih-tzu yes it is. i have 2 and they both snore at night. she will be fine and yes you have to be very careful with overheating are's are out side for 10 minutes and have to drink a ton of water and are panting hard. your shih-tzu will be fine :)
***Edited By: Rescuepup on 12/28/2006 1:33:35 PM*** Reason: sp
She's a short-snouted dog, so the breathing problems are normal, as others have said. I have a Lhasa Apso that had breathing problems, he panted alot, snored at night, snorted during the day, and had trouble sleeping for more than 5 minutes before waking himself up. I switched his food from Eukanuba Puppy to Innova, and his breathing problems have disappeared. So, I would make sure you put her on a really good food.
Many Shih-tzus have the "pinched" nostrils when they are born. Most outgrow them and the nostrils tend to widen as they grow. In severe cases, that don't widen by themselves, the vet can perform a procedure (surgical) to widen the nostrils.
You have to watch to make sure the dog is taking in enough oxygen with the pinched nostrils. Have you spoken to your vet? They can diagnose the problem much easier than us, since we can't see the dog.