My cat allways start to groom itself when I pet it. I can start scratching it, and it instantly starts to lick itself. When I stop petting, the cat stops licking instantly. I can pet it for 2 seconds, and my cat will lick itself during those two seconds and then stop after that. It will start licking instantly itself even if it was very chill and almost in a sleeping state when I started to pet it. I really wonder why. Does anyone know about why he does this?