2000 Volkswagen Jetta Question: Why my car revs out when i hit 2 on rpm.

When drivin my car once it goes to 2 rpm's than it will rev to 3 4 5 until let go of speed. Sometimes it does shift the gears and when it does it does very smoothly. No engine light is on. How can i fix it . What is wrong? Bugs me cuz just bought a year ago