I second asking the vet. I'd suggest making sure the attacks are random, and not some pattern or some behavior that spurs it. For example: my cat will be totally happy lying on my lap, sleeping even, and acting so sweetly, but then if I move my arm in a certain way (like flipping a page a way that annoys her or typing over her) she'll attack. Or if she's lying happily on the couch/bed next to me and I have my ankles exposed..bad news there (I have to cover them with a throw or something).. Or if someone walks past her in the hall wearing black or gray socks, she'll attack. And, like you, it's not just playful (after a while the hallway attacks just become amusing.. like, come on, you're a 6lb cat lol).
And wow, the coincidence, real-time example, my cat just wandered up onto my lap, purring loudly, but.. she is lying over one of my forearms, and despite how happy she is this very moment, I know from experience that if I keep typing without extracting my arm pronto (involves distracting her with petting from my other hand and carefully removing the arm she's on), I'm going to have fresh teeth marks in my wrist..and now my arm is removed and we (cat and I) are both happy.
So, if your Beans is like my cat, and there isn't some underlying medical condition, and if you can somehow learn more about the patterns, it'll be completely worth it. Mine is 16 and she means the world to me, despite being this way her entire life.