Ball Jittering Problem !!

Hello, I am a newbee in Unity world, I am building a simple pong game where user serves the ball and scores a point if the ball reaches the opponent's goal post. However I have a problem in the ball movement. The ball movement is not smooth, it is jittering dinn know why. Here are the methods I used.

1) Used Interpolate. 2) Used fixed frame rate in the code. 3) Used the code in fixed update.

Attributes attached to the ball are - 1) bounciness Material. 2) ball gets a velocity when collides with the paddles 3) Velocity is normalised. 4) Sphere collider.

Any help is highly appreciated.