I had that sound from my car a few months ago...dead battery
but since u changed urs i don' t know if its the same thing
this is what my car would do)
-first time u start it up it would hesitate alot then finally crank and start up fine
-when it died....when i went to start it...it would just make a tic tic tic sound and nothing happened
the E420 has 1 battery in the trunk correct?