Perhaps you’ve noticed that relief pitchers in baseball warm up by making a few slow motion “pitches” without the ball and then stretching their arms when their muscles feel warm. Their first real throws are slow and controlled, with little spin. You should do the same thing on your serve.
First, take a few practice serves without the ball, including a practice (pretend) ball toss. Stretch your muscles when you feel warm and then hit your first serves slowly and in the middle of the box with no spin. After you loosen up, increase your power, put more spin on the ball, and begin to move the ball around. If you copy a relief pitcher, you won’t need relief yourself after your match.