2003 Audi A4 Shaking alittle while accelerating

Yes I just bought an Audi a-4 4 days ago. Im starting to notice alittle shakin when I accelerate after 2nd gear. When im going 50mph, I'll let go of the gas and it'll cruise smoothly. but when i barely touch the gas to accelerate, it will shake alittle. Im not sure if its been doing that since I bought it or if Im just now noticing it...