BMW 645Ci misfire

[volvos60s60]

Hi. I have a 57000 mile '04 645 Ci with a misfire on 4 cylinders, which only happens when cold. If I turn off the engine & restart after 30 seconds, all is fine. I have fitted new spark plugs & crank case breather vent valves so that is ruled out

I recently had to replace a faulty voltage regulator. Is is likely that a faulty voltage regulator may have damaged some coil packs?

Thanks