Thanks guys.

Well I had the auto parts store check my battery. It showed good and so did the starter and alternator using their tester. So I stopped by the dealer to have them check for an unauthorized amp draw. Their tests showed good battery, starter and alternator as well. I only had a few milli-amps draw, appropriate for maintaining the clock, memories etc.

He said with a battery this old, (original over 4 years, with 110,000 miles), it is probably sulfation and I should get a new battery. I went ahead and just got another battery like the one that came with my XK for $150. They cleaned the terminals etc. I had good service with that battery and if this one lasts that long, I'll be happy.