I agree with Scudder, the VANOS sounds like it could be the problem. The VANOS system normally activates in the high rev’s but also activates during cold starts to warm the car up more quickly. There are several gaskets/seals in the VANOS drive that wear out around 4-6 years of age. There is a kit available to redo those yourself if you are mechanically inclined, or the dealer should know about that problem. After replacing said seals, you should also regain some of that acceleration you may have noticed your car missing lately.
But, it could be something simpler. You didn’t describe the “won’t start” malady, but it could also be something as simple as a tired cold battery.