Loraine, my cat does the same. She's like your cat, very affectionate and sweet most of the time. But I never know when she attacks me. I got her from a shelter 5 1/2 years ago and from her behavior we (the vet and I) think she's abused by her previous owner. I've tried everything, including meds but it doesn't help. Right now she's on meds again but she still attacks me. Only solution is putting her down but I don't want to do that because she doesn't deserve that. But I have to admit, sometimes I'm so fed up with her behavior!