Tip of cats tail moving, cat very lethargic not eating, drinking little water

My 14 year old male cat has become very lethargic in past 24 hours or more, he isn't eating, drank some waterthis morning. The tip of his tail is moving.

You need to get your cat to a vet.

It sounds like he's sick. You need to get him to the vet.

The tip of his tail moving says very little about his condition. The more important points are the lack of energy and refusal to eat. Make sure you tell the doctor about those, first.