Pick-up problem

I had a 2002 skoda octavia mk1 rider variant. It has 1.4 lakhs km on the clock with propeer maintanence. I crazy in driving and always test the car while driving it. It gave me a huge fuel efficiency on the MID. But the problem in my baby is when i press the gas pedal the engine rpm gets increases but the vehicle does not moves. One day i used to make a rash and noticed that after a particular period of say about 2500-3000 rpm my car give me a sudden jerks and gets picked up and ran fast. After the jerk it gives me a good pick up ride. And also when i stop it and turn off the engine and started again the same problem arises. Again i have to reach 2500-3000 rpm in 2nd or 3rd gear and have to get the pick up. Please suggest me of good solution to arrest the complaint.