There could be several reasons why a cat might suddenly bite its owner. Here are some possible explanations:
Play and Interaction: Cats are active and playful animals, and they may use biting as a way to play and interact. Sometimes, cats will gently bite to express their excitement and happiness.
Social Behavior: In the feline world, gentle biting is a social behavior. Cats can exchange emotions, build bonds, and demonstrate their dominance by gently biting each other. Sometimes, a cat may gently bite its owner's hand or foot, attempting to establish a closer bond and express dependence.

Teething period: When kittens are about 3 to 6 months old, their baby teeth will begin to be replaced by permanent teeth. Kittens in the teething period may bite people because of itchy teeth.
Feeling anxious or uneasy: When cats feel anxious or uneasy, they may bite to seek comfort or express their dissatisfaction.