You don't prepare for the swing until the last instant, which forces you to rush the swing in a jerky motion. You start by turning the shoulders early enough, but then you wait to complete the takeback until too late. Then, at the last instant, you yank the racquet back quickly and then jerk it forward into the ball.
If you watch pros, they all use a high takeback, with the head of the racquet at or above your head. And they get the racquet to this high takeback position early (usually lifting the racquet at the same time as the unit turn). Then, from the high takeback position, they usuall start the swing simply by rotating the body toward the ball and letting gravity sweep the racquet forward like a pendulum. Finally, from the bottom of the swing, they accelerate the racquethead to drive it forward with power through the hitting zone.
If you stay slow and relaxed through the takeback phase of the swing and the racquet drop part of the swing, it will feel more smooth and natural when you accelerate the racquet forward on the final "driving" part of the swing.
Question if you may, when you stay low, does it mean you bend your knees at a say around 15~20 degree and use the leg drive to pounce at the incoming ball while swinging through the shot?