2002 vw jetta starts decellerating

I have a 2002 VW jetta ... sometimes randomly when i drive the car it all of a sudden starts decellerating... i take my foot off the gas then press it again and it jerks and starts accelerating again, also ... i have stopped @ a light twice in the last month and it just quietly turned off. whats wrong?... also i have a light that randomly comes on and off.