Welcome to the club, Donovan.
The s type is a great car, and its good to see younger people appreciating it.
However it is susceptible to niggles in the electrics if the battery is not up to it. The life of a battery is about 5 years, and I changed mine at the end of December when it was 4 years and 10 months old, as I was having an electrical problem. Problem cured immediately. The s type will shut down unnecessary electrical items if the battery is failing.
On the other matters, my engine is the 2.7 diesel -- quite different from the 3.0 litre petrol, but you will get some assistance from other members.
Regards,
Peter.