Well you need to isolate where the sound is coming from, possibly with an assistant and an auto stethoscope or the ol' screwdriver to the ear trick.
How many miles on the car? Starter sounds like a good bet - gunked up pinion gear shaft or overrun clutch. Could just need cleaning, but depending upon mileage, rebuild/replacement may be the most cost effective fix.
Being intermittent, it doesn't sound like variocam issues to me.
