yesterday I started the engine of my Mercedes C220 W204 (2007) without any problems, I passed few kilometres and when the trip ended I switched off the engine. I noticed very loud clicking sound in the frontal part of the car on switched off engine, see the youtube video. The clicking sound gone after 10-15 seconds. I put the key again and turn on position 1 (no any sound), but on position 2 that annoying appeared sound again (the car is still not started).
Watch the video that I made: https://www.youtube.com/watch?v=s_4SSTJdTKc
Today I put the key in position 2, and there is no clicking sound, everything is normal.
Passed two months I was hearing this sound shortly and periodically only when I was preparing for starting the engine, but yesterday it was pretty loud and longer.
I checked both fuse boxes but the annoying sound not coming from some of the relays.
Is it something that I need to be worried, and do you have any experience with problem similar to this?