Why is my dog growling?

[davidlynn86]

I have a new dog, who is very sweet to people and my other dog, but he is laying down resting or going to sleep, he growls really loud!! It sounds almost like he is snoring. No one bothers him, and if we talk to him or pet him he gets all playful and happy. It's only when he's resting or falling asleep and NOT being bothered. Does anyone know?