Why is my dog nibbling while sleeping?

Right now my dog is nibbling in his sleep. It's quite amusing, but what do you think is going on :)? Also, do dogs normally twitch and whine in their sleep? Should I let them be?

My dog sometimes twitches in his sleep, so I'm pretty sure thats normal.

Dogs, just like humans, dream. They may appear to run, they may yelp, they may twitch, whine or any number of other things in their sleep. My beagle does these thing all the time. It is perfectly normal. You did not give the age of your dog, but if he is a puppy he may be teething and his teeth could be bothering him in his sleep. When my dog twitches and whines, my instincts tell me he is having a bad dream. Since he sleeps with me, I just reach over and stroke him gently and tell him its all right. He usually settles right down and sleeps calmly again. If this is a persistent, every time he sleeps habit, you may want to have the vet check his teeth and make sure everything is in order in his mouth and there is no medical reason for the nibbling. He could just be dreaming about food or his favorite chew toy!