Okay, everyone has beaten you to death about the OVP being the source of your problem, so I will add my two cents worth:
No, a faulty OVP will not show up on the fault codes, and the intermittent failure will cause hard starting problems, stalling (especially with A/C on), ABS light coming on, etc.
I just replaced mine a couple of months ago (at the suggestion of this forum), and it solved problems similar to yours. (What a great forum!)
As far as everything else:
Definitely go back to copper plugs...my VW hated the platinum ones too, and I switched to copper Bosch plugs (must be a German car thing).
Just like trying to fire up the lawn mower after a long winter, unstabilized fuel in a vehicle will cause problems...had to rebuild carbs in my Bug after unintentionally storing it for five years!
Extremely short trips will do more damage to the engine than you can imagine...take a long route whenever possible to your destination.
Otherwise, it's a great car! Makes me proud to be able to work on it myself!
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car