Nothing happens when I turn the key in my E500 Wagon on 2005 Mercedes-Benz E500 4MATIC

Noticed this a few days ago... After sitting overnight, I got in and turned the key... Everything lit up fine (dash, display, etc.) but the car didn't make a sound. Turned it off and back on and it started. I parked at the office and came out at 5pm and the same thing happened. Over the next couple of days, I noticed it was more likely to happen when the car was cold or had been sitting for 6-7 hours.. A few times I had to try 3-4 times before it started. When the car's been running, it seems fine - no problems. This leads me to believe I have a weak battery, but I get NO battery warning lights, no "consumer" messages, no dim lights - no other signs/symptoms I replaced the battery today with a Bosch - simple swap and hope this resolves the problem. If anyone thinks it might be something different, please let me know (hope not, the extended warranty just expired) Thanks

by in Howell, NJ on November 18, 2010
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2 answers 1 comment
ANSWER by , November 18, 2010
It would have been a great to have had your Computer System scanned before you disconnected the battery because there would have been a failure record that would have led you to the culprit. Your car has DOZENS of computers in multiple networks, that have very sophisticated 'flight recorder' type systems that catch and record even very subtle problems.
ANSWER by , November 19, 2010
You needed to replace your ground wire!
COMMENT by , November 19, 2010
What ground wire? On battery?'re taking to a handy guy, but not a mechanic!