Why is my cat suddenly biting me?

Perhaps another person moved into your apartment with a cat of their own. He could be feeling anxious about his territory. Or he knew you were leaving when he saw you packing for your vacation and that made him anxious. And his reaction to being anxious could be to start biting. Since he is an older cat he could be in pain from something. This pain might make him anxious or more aggressive and so cause the biting. Or he could overly excited by you leaving and coming back. Some cats when they get over stimulated will nip.

I assume that the bites aren't very hard and he lets go right away. If he is trying to take a chunk of flesh out of your hand he is then horribly stressed and could be horribly ill.

A tip is to gently encourage him not to bite. Don't yell or give a big reaction. Just gently push him away or stop him and otherwise ignore the behavior. Cats will continue a behavior if you give any strong reaction whether positive or negative. So ignoring it will teach him that there is no payoff to the behavior. You can also try playing with your cat with an interactive toy. A toy on the end of a string or stick is good so he can't bite your hands. Giving him a good solid 15 minutes of play time every day will drain his energy in a positive way and leave less energy for biting.

If the biting gets worse and doesn't improve, I would consider taking your cat to the vet for an exam. Otherwise it's probably because the vacation upset him.

My cat is 13.He does that for no reason at all too.I lye in bed and try to be nice to him and all of a sudden a big bite comes my way.I think when they get a bit older,they do that at times.

normally if a cat is all of a sudden biting you, its due to rabies. but i dont think a rabid animal will sniff and bite, just bite and attack.