Electrical / starting problems

[Andy N]

Hi Folks having a bit of an issue with my wifes 2007 C200 Coupe Cdi, If i put the key in the dash i can hear the steering lock come off , all the dash lights come on as they should , i can start the car however at that point the gueges all go to zero , there are no wipers indicators or electric windows , however the interior and exterior lights come on also the radiator fan kicks in too , beginning to think the car is possesed . Any help greatly appreciated