So, I haven't been able to post any advice for while since I no longer own a Mercedes, but this will apply to all owners with newer keys that are straight on the edge and have the groove in the middle that moves the locks and ignition.

Be sure that your key doesn't build up lint from your pocket or it will collect in the ignition and eventually ruin it! I was stranded last week in my VW because the key wouldn't turn in the ignition. After having the car towed to the shop and haveing them check it out, I was told that lint build up in the key had collected inside the ignition to the point that it could no longer turn. They cleaned it out and re lubricated it and it works fine again. But if it had been left much longer, I'd be buying a new ignition. Now I just make sure that there's no lint in the key before starting the car.

Hope this helps!!

__________________

Current:
2014 VW Tiguan SEL 4Motion 43,000 miles.

2016 Hyundai Santa Fe Sport (wife's).

Past:
2006 Jetta TDI 135,970 miles. Sold Nov. '13.
1995 E-320 Special Edition. 220,200 miles. Sold Sept. '07.
1987 190-E 16 valve. 153,000 miles. Sold Feb. '06.
1980 300-D 225,000 miles. Donated to the National Kidney Foundation.
1980 240-D manual, 297,500 miles. Totaled by inattentive driver.