2006 bmw m3 valvetrain noise on cold start

A few, What does your oil look like, has it been changed religiously, what kid of oil are you using, oil pressure, are valve solenoids good, restricted oil flow to vanos. Without testing, all are possibilities.

An occasional ticking or rattling noise from the camshaft hydraulic valve lifters (HVA) may occur during cold engine starts, due to frequent short - distance driving, or the noise may occur for an extended period of time even though the engine is at operating temperature. Improved parts were phased into production beginning on 10/1/2008 and fully implemented on November 31st 2008.