Intermittent starting problem E320 cdi w210

[L_A]

I have a intermittent starting problem that seems to getting worse on a E320 cdi. When starting the car sometimes it is totally dead when trying to fire up, i hear a click followed by a bit of clattering from under the car then a slight "BANG" noise this was happening every few days however now the car seems to be totally dead when trying to start up, does what i have described above and some times if i am luckily starts straight away. Any ideas of what this could be as it seems to be getting worse?

 

[proser]

Sounds very much like the starter motor solenoid not fully energising and therefore not locking off into the flywheel.

 

[alexander patie]

as above, possibly destroyed the ring gear now. a stitch in time saves nine.