All the flaps move to a park position, the injection pump shut-off
makes some loud noises, the glow relay will click a time or two,
the valves for the heater box positon themselves, relays in the
fuse box close, the K40 relay clicks loudly shutting of ABS and
the Transmission controls......ect.ect.ect...
There is all kinds of goodies doing their stuff under that hood
when you cycle or shut off a E300 fuel system.
I wouldn't be worried.
DR.D