The cables are good and tight, and the negative cable is solid, showing no corrosion. However, just to be sure, I removed both cables from the battery, cleaned the connectors and battery posts, applied silicone dilectric grease and tightened them again.

It seems that now it's always taking at least a couple of tries to start, even from cold, and when it does start it stumbles and sputters for a bit before smoothing out to a normal idle.

Last night I drove about 30 miles and as I was parking the car it stalled. When I turned the key to restart, it was the "totally dead" thing again. No warning lights on the dash, no buzzers and of course no cranking from the starter. I kept trying to restart about every 30 seconds for 4 or 5 minutes, but with the same dead results. Finally, I got out of the car to see if the headlights were on, (daylight and raining), and they were. When I got back in, everything was back to life and it started as it always does, several trys to get going, then spit and sputter for a bit, then settled down to a normal idle and ran fine.

__________________
2000 Mercedes S500
1990 Mercedes 560SEL
1970 Triumph Spitfire