I got my guinea pig about a week ago so I am still kind of new at this. Today I was lightly brushing my guinea pig on my lap. Every time I would brush him he made this purring noise and his whole body shook. He never did that before, is that a sign that he is enjoying it or not. He wasnt trying to get away from me or anything either. But I put him back in he cage he went straight for his little house.