Based on research this is more of an issue with the s54 engines. There is about 4mm of material between the cylinders of the s54 and s62 engines, so there is not much gasket material there either. The cause of this could be several reasons... lean mixture, faulty gasket material etc
The rattling sound, under medium throttle in higher gears at lower revs produced a rattling type sound for many of the S54 owners, and I could only find 2 concrete examples of other s62 engines with the same symptoms that turned out to be the result of HG failure between the cylinders. I was lucky enough to find a sound clip of the rattling sound from one of the S62's with HG failure. I've added this as a play list with my sound clip to compare the sound, and it was quite the same.
S62 head gasket failure :
S54 head gasket failure :