My Mainecoon (neutered) boy has started with a strange behaviour.  He's biting people.  So far it's only been my In-Laws so nothing serious but I would hate for him to think this is OK.  The first bite was my SIL and he bit her on the throat and he bit my FIL on the hand yesterday.  Today, my daughter was cuddling him which he didn't want and I was in the process of telling her to let go as he was fed up, and he turned round and bit her hard on the head.  No damage anytime but enough pressure to leave teeth indents.
Any ideas why he would suddenly start to act this way?

Well it is normal behaviour for my boy Dave as he loves a good bite and Pokes his big sister also bites when provoked but if it is unusual behaviour then perhaps he is in pain and trying to stop people cuddling him maybe ?

if it is unusual for him and he is past kitten stage could there be a chance he is in pain, and that someone stroking him is hitting a sensitive area?

How old is he?

In my experience, cats who are adult often don't like being cuddled unless on their own terms despite putting up with it as kittens/youngsters.   Sounds to me as if he is letting you all know he's all growed-up and wants some respect?

Of course I'd also check out whether he's in pain first, but if given the all clear...

Unwanted cuddles is perfectly understandable -most cats would react that way. But otherwise -what were the bites like? Slow or quick? I can't help but wonder if it's mating behaviour. Neutering doesn't necessarily stop it and it can appear after years. But I would also echo a vet check -didn't you say he goes outside? He could have a bite wound or similar hidden deep inside the coat. Easy to miss. He could also be in a generally bad mood if there is stress from other cats outdoors.

I would get him checked by the vet to make sure he isn't in pain as it's  a new behaviour, just to make sure.

My cat is a biter, but she merged into that behaviour as she grew out of being a kitten :( She's an evil little cow! She'll sit next to my keyboard and if I 'dare' touch any of the keys near the end she's at she'll attack me If I try and move her away, she'll attack me! She is better than she was and will occasionally allow herself to be stroked on the head once or twice.
She only ever bites and scratches hands/arms, she'll even wrap her self around a sleeved arm (all 4 legs gripping on with claws) and try to cram her head up the end of the sleeve to find flesh to bite

Sometimes she'll curl up on my lap, she looks so pretty and her long fur is soooo soft, but I can't touch her or she'll bite me.

She attacked my dad yesterday, we had gone out in the garden for a ciggy, on the way back in he was behind me, she didn't recognise him so she attacked him. My poor dad nearly fell back out the door. Luckily he stepped back quick enough to avoid injury, but the sound nearly gave him a heart-attack. When she realised it wasn't an intruder, she ran to her food bowl and mewed at him for some food!

Gosh, I think if there ever was an intruder in our house, they'd have to get past the cat before they even met the dog :-D

LOL, Mastifflover!! I LOVE your cat.....Cat with attitude=my kind of cat.

IT is a new behaviour and he is 8 yrs old.  He only bites when they have been sat petting him and then stop.  He will then give a slow pressure bite.  Is it to get them to pet him again? If so, it doesn't work!!  My FIL states that it's because I've moved him onto a raw diet and it's bloodlust!haha. If only he'd seen all the poor headless mice over the years!

hi I have the same with my long furred male cat. He goes out alot and comes back with knots in hisfur :( which I have to either brush out or cut out :( poor thing, he hates it and is in so much pain when he has them (only in summer) that has made it so he does not like being stroked as he is worried it may be painfull, nd although he has never bitten or scratched me he has to others who give him a stroke, so maybe your cat is in pain.

But again you said it is when the person stops stroking ????Bit weird he is 8years old and only just started doing this ?? My other cat does this but has done since a kitten (he goes the hole mile if u still persist in not stroking him and grabs on all 4 claws roand ya arm, but funnily enough no claws out haha he is a weird un) Maybe yours is just getting more grumpy the older he gets, and more demanding that he wants things his way (hence biting when he wants fuss). He may have done this behavour once, found that it got him what he wanted and so carried on doing it. Im not an expert but tht is my opinion :)