Hello, such symptoms usually indicate faulty key or ignition switch. If you have a spare key, try to use it. If this does not help, voltage supply of the ignition switch will have to be checked. If there is one + and one ground, ignition switch itself is bad.
Let me know if i can help you more on this
This took too long for a reply - which conflicts with what Mercedes have told me in the meanwhile.
Sorry, i replied to you as soon as i saw your question. I would appreciate if you let me know what was done to fix the issue.
You can have the question closed without being debited, your deposit is in your account on the site.