Misfiring engine

Help: 2008 328i Two weeks ago, engine suddenly misfired consistently with lack of power, and the CEL came on. Lucky it was the weekend. Cheapo OBD 2 showed PO301. I narrowed it down to the #1 coil pack (integrated with spark plug connector). $80 later and she purred like a kitten. Next day, CEL reset itself, and she ran like a champ until tonight. Now it's misfiring again, and the OBD codes constantly change (U2500, POE8C, POE68) and others that don't make sense, or aren't listed. I was expecting P0302 - P0306.

Anyone have any ideas? When I bought the new coil pack from the stealer, parts guy asked if I wanted one or six? I only bought one as I didn't think these were a routine replacement. I also didn't want to spend $400 needlessly, which is the stealership's M.O. This car still has under 40,000 miles, but is beyond the warranty in age (Nov. 07)

Advice is appreciated!

I`d check the battery power levels then replaced the plugs and all the coil packs.

That's next. Thanks!

Resolved:

#3 coil pack was the culprit this time. Parts guy (they're advisors now) at Stealership and Leekay are correct: If one goes, replace them all as the rest are getting in line to take a dump. In this case, only 10 days apart. I'll now buy the remaining 4 from Bavarian online and have them ready when the time comes.

Per BMW tech I met, no worries if you need to drive a bit on 5; car automatically shuts fuel off to the misfit cylinder.