while driving at 55 mph, the car started hesitating and dropped down the 40 mph then accelerated up to 60 mph
its either a vacum or thorotal body issue. First i would change all the plugs and wires if you have not done this in over 100,000 km or more. Next clean the mafs (Mass Air Flow Sensor). Hesitation like this could also be fuel related such as the fuel regulator or your pump or even as simple as a cloged gas filter. The best thing you could do is bring it to a vw specialist and have them scan the car with there rosstech software since the car should have registered the fualt in the computer they should be able to help you faster then we can.
Search Volkswagen Beetle Questions
Volkswagen Beetle Experts