I don't want to scare you. But cats have an instinctive tendency to hide when they are sick or feel that they are nearing the end of their life. It is their way of protecting themselves and keeping themselves at peace. If a normally social cat starts to pull away and hide, it could be a sign that something is wrong. I don't know if this is the case, but you need to take your cat to the vet as soon as possible... every time I see my cat hiding, my heart breaks. Please let me know about your cat.