I have an older rescue cat that acts somewhat the same way. Ghost will let me pet him until HE decides he's had enough. He'll swat me if i don't recognize his body language soon enough. He likes to sit with his chest on my leg, but I have to watch where and how long I pet him. I call him a cranky old man.

Maybe your cat is satisfied with a little petting for now. Give him time and he might want more later. I agree with saying "no biting" and walk away.

Mary