Hi, I had the same problem with my old 200tdi.
If you look at the rear of the battery a thick brown wire runs from battery over inner wing and splits into 4 seperate fuse wires and then back into 2 brown wires ( think from memory). they may be taped up or covered in some way . Jiggle them about...
More than likely the fuseable links near battery. My 200 tdi had same symptoms. I cut all connections out and replaced with new crimped connections and had no more trouble.
HI, just noticed a whining noise under bonnet, not too loud but seems to be coming from water pump or alternator, is there anything else that could whine under there.(My wife could but theres no chance of gettin her under the car!!).
Thanks