I don't remember if that plane is a tail dragger or trike.

If it has a nosewheel, the problem could be as simple as your rudder and nosewheel not being aligned with each other. So while rolling, the wheel keeps you straight and overcomes a rudder that is actually out of trim, but as soon as the wheel leaves the ground the rudder takes over totally and the plane turns. Usually when I see this with students' planes the effect is rather small and doesn't cause a problem, but it might be worth looking at.