cat goes from very friendly to biting and scratching?

My cat does that too. cats are just like that sometimes. They wanna be petted and then they suddenly decide "I CHANGED MY MIND GET OUT MY FACE!!"

Thats just how cats are.

Not all cats are like that. I have 4 cats, 3 of them are very sweet and loving, the forth one is part siamese and she acts like that. I had a neighbor who had a full blood siamese and she was like that too. Just be sure to say "No" when he does bite and scratch you so he knows its not acceptable behavior, otherwise he will think its ok to bite you and do it more often.

It may be a dominant behavior. My male cat used to do that. Many cats do. But the thing you have to do is BACK OFF. Let him come to you more often, don't be so intent on trying so hard with him to win his affections. It backfires in most cases. Ignore his frightened behavior (don't even look at him to acknowledge him) in the sense of don't try to sweet talk him or win him over. That seems to add fuel to the fire. Ever wonder why cats are drawn to visitors that don't particularly like cats? But do walk softly and quietly and at a slower pace without sudden or jerky or loud moves. Regarding the biting...This is likely a dominant behavior, since cats have a heirarchy just as dogs do. Pay attention to his behavior, his body language (eyes dilated, ears slightly back, looking gradually annoyed, tail flicking even the tiniest bit, head pulled back like a turtle) as these are signs he's going in for the bite or grab and bite. Keep his nails trimmed, and work on your own reflexes (so you can get your hand away before he gets you!). But seriously, you should already be aware he is going to try something when he starts acting waay too "affectionate", rubbing hard and forcefully against you with his head and cheeks and body, because this behavior is more of a dominant thing since he is scent marking you with the glands in his cheeks, not truly seeking petting. This is also accompanied by loud vigorous purring. If he bites you, say "tsh!" sharply (not angrily) and put him off the couch or furniture. You can also keep a squirt bottle handy, but never threaten with it and only 1-2 squirts then turn away and ignore him and pretend it wasn't you (conceal or immediately put down the bottle). Also, never allow your cat to push you out of your spot on the bed or chair, as they may try biting you to get their dominance and point across. My male used to bite me when he was hungry and wanted food, when I was sitting on my bed (his favorite spot), etc. I used to give in until I finally got fed up and realised what was going on, that he was the dominant cat in the household because I let him. I'm now top cat in this household, as should you be. He has mellowed out, and he is sweeter with age (about 4 yrs or so now), but I don't pet him the same way I do with my female cat who does not usually bite. I pet him, but I don't over-pet him at one time, and I pay attention to his body language and signals. Neuter him if he is not already. Spray bottle......

i think its i nalot of cats nature to change there mind! but not to that much of an extreeme! maybe he's going crazy or has bipolar! but i know alot of cats that are like that.. theyre all like peeet meee muah muah muah and then RAWR! with the nipping and the swatting. i think its just sometimes part their nature.. like also how they cant decide whether they want to go inside or stay out and they stand in the middle of the door and house for five mins while your freezing in the doorway haha

My cat does that I think she is nuts I dont know what causes it but I just deal with it