So I have a rottweiler who is not even a year and a half old. He is very nice and gentle and has never bit anyone. Well... about two weeks ago my fiancee took him to get his nails trimmed. He only had this done to him one other time (when he was a puppy). She said he was terrified the entire time, crying, whining, etc... The other night, it was kind of late and I was laying down with him. I grabbed his paw and started to pet it and he growled at me.. I said wtf? So I did it again and he snapped at me but I moved. What should I do? This isn't cool.