Why does my Jaguar '02 s-type 4.0 take so long to start then won't start at all. Key Transponder...or Computer?

Your problem is that you spent approximately $78,000 on a vehicle as a status symbol and you do not know how to work on it. I spent approximately $13,000 on my Chevrolet and I am able to easily maintain it so it works fine. Good luck with that!