One problem related to car accelerates on its own has been reported for the 1997 Audi A6. The most recently reported issues are listed below.
1997 Audi A6 unintended acceleration - stuck throttle. Only way to stop car from moving was to turn off ignition. Audi dealer (suds - normal, illinois) found ice in throttle housing and was familiar with problem on other like-model Audis. If I did not have presence of mind to turn off engine I would have run into cross traffic on busy six lane highway.