The problem could be the lock for the steering wheel. Move the steering either side while trying to turn the key.
Your ignition switch crapped on you
Unlock the ignition? Is the key not turning? This car has a steering lock, but if the key is not turning you probably have either a bad key or a bad EIS (electronic ignition switch) make sure you check it with BOTH keys first, if you have another one.
hgtjjhjuhhjhhjjhjhhj
leave the key in the ignition over night key should reprogram
can not removed key
Do you have the "valet key" (black FOB key with the auto-lock & 'panic' buttons are)? We had this problem with our '98 E320 and it turned out the battery in the valet key needed replacing.
It probably is not the key. It could be the battery or starter. Try lubricating it with powered graphite. If that does not work then the ignition tumbler assembly may need replacing. They do wear out over time. Of course you may be using the wrong key.
Either something is wrong with the key or there is something wrong with the switch. You can try to spray some WD-40 or something like it into the switch and wiggle the key to see if you can get it turning. Otherwise you may have to replace the ignition switch.
Wrong key?
By turning the ignition key...
So it would seem. If the ignition is in the column it may also be jammed by the steering wheel lock. Try turning the steering wheel and holding it while turning the ignition key.
It's the wrong key maybe!