Frankly the W210 E55 coils and wires are generally good out past 200K miles - although sometimes rarely a individual coil can go on the blink - hence the good advise from the earlier reply.
Also a great time to check the general condition of the plugs - replacement Bosch OE equivalents are very affordable and a good afternoon DIY helped by a search for DIY photo's and instructions on this forum.
Intake issues (dirty air filter and dirty MAF) start off by triggering a misfire on a individual cylinder, then kind of spread by triggering sporadic misfires on other cylinders that same side.
That said - also a good time to consider putting in a new Mann air filter for like $16, and a good cleaning of the MAF with a can of $9 MAF cleaner.
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