Why Does My Cat Bite Me For No Reason?

If your cat is biting hard/drawing blood, this is something to be concerned about and discourage. This could be because the cat needs more play time, or because he/she is over stimulated.
When playing with your cat, use a toy. If you allow your cat to bite you during play, they may transfer that idea over to when you're not playing.
If your cat bites you and is on your lap or in your chair, put the cat on the floor and ignore him/her for about 10-15 minutes. This tells the cat that biting gets no reward. Saying "ouch" loudly (or making another loud noise) also helps the cat identify the inappropriate action.
If nothing else works, use a spray bottle. Gently squirt your cat in the face just enough to shock the cat, not soak him/her. This tells your cat that biting gets an undesirable result.
If your cat is nipping, this is a different story. Is your cat nipping you when you're petting him/her? Cats will nip you to display affection. If you'd like to deter this, any of the above methods will work, but do remember that your cat is doing this out of love.
Lastly, don't hit your cat. Violence brings violence.

If he or she doesn't appear to be angry,they're just doing it out of affection. My cats do that sometimes. If the cat looked angry he/she might not be feeling well or maybe has an injury and is just reacting because they're in pain. Sometimes,if you are the closest one around,they'll just bite because they want to be alone. So I usually put them in a room by themselves until they've calmed down so I can see if there is a problem.

Your cat probably is hiding something from you. Maybe he/she is trying to send a message to you saying that he/she is hurt, feels lonely, depressed or he/she might feel sick. If he/she starts throwing up or looking at something for more than 5 minutes, talk to your vet as soon as possible. It could probably be a sign of sickness or death. If it's not a sickness and he/she is harming you, it's best to try to stay away from your cat until he/she cools down. It could be fear from you but not everyone else. It might feel uncomfortable around you or scared.

If its young probably teething