Thanks, Jim, Jim, and Dean. The tech who is looking after my car had similar codes read, and is currently just clearing, recreating the fault, and re-reading to try to find a pattern. I called him about the alternator spikes, and he is aware of that unit being on the list of suspects. He has been looking at the alternator readouts when the diagnostic unit is plugged in, as I understand it. So far no problem there.
1995 E320 Wagon Moonstone Grey/Parchment 106K mi.
2007 E63 AMG Graphite/designo 75K mi