I'm sorry 400E, I forgot to answer that question! No, my 1995 C280 does not have the "SmartKey" (TM). They started the SmartKey in 98 for the 202 chassis.
So I'd rule that out as being a culprit.

But it was so weird... yesterday morning, it was 18 dF in the morning when I started my car (BLIZZARD!!!!). It was really weird... because I cranked it for like 4 seconds, noticed that it didn't start, and then when I released the key (/starter), it caught and started right up! After a short drive and coolant temps about 50 dF, I restarted the car after stopping, and it started normally (cranked for only a second or two, me releasing the key when the engine caught).

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)