2000 Volkswagen Beetle stumbles after starting

First of all, is the check engine light on? The cheapest and likely guess on a volkswagen is the coolant temperature sensor, which should be under $10.00 at the dealership. Any parts store should have the same sensor in stock, just make sure to get a new o-ring and clip. (or don't lose your originals, pray for no leaks.)

Also, pull the engine cover off and inspect the vacuum lines off of the intake manifold and fuel pressure regulator.