Typically, a ball is topped because the club has not gone far enough down towards the ball or you catch the ball on the way up, instead of at the bottom point. A lot of things can cause this to happen: A club that’s too short. An awkward stance.
What causes you to top a golf ball?
Lateral motion in the backswing moves the swing arc backward. If it isn’t then moved forward in the downswing, the low point of the arc is behind the ball, often causing a thin or topped shot.
Why do I keep topping the golf ball with my driver?
As you approach impact, you lose your original address posture and spine inclination to the ground, which causes you to practically swing over the top of the ball. This is often caused by the urge to help the ball into the air.