Every once in a while, my key won't unlock the doors. After a few tries, it works. Other times, the key unlocks the door. I insert the key, the car recognizes the key (I hear the click), I turn the key, the engine bumps for a fraction of a second, the nothing.

Once this happens, I have to turn and hold the key in the start position for a few seconds. The car then starts, but the ESP light comes on and the display tells me the car needs service. I turn the car off immediately, and it will restart right away, and the warnings are gone and everything is ok.

This happens with both keys. Any ideas? I don't think it is the keys. Something in ESP?

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Thank You!
Fred
2009 ML350
2004 SL600
2004 SL500
1996 SL600
2002 SLK32
2005 CLK320 cabrio
2003 ML350
1997 C280 Sport