Does the car go into gear with the engine off? I would take it to a dealer ASAP, could be any number of things from tranny to shifter to something not obvious like a broken motor mount. Any info you can provide to your dealer will assist them in diagnosing the problem. A little information like when it started, did it get progressively worse, or work one day and not the next. Does it make any unusual noises while moving, while the clutch is depressed, etc. Can you shift into first but not second? I assume you are going from 1st into 3rd. Get Megan involved. She will need your mileage, VIN and dealer name.