Why is Spaceship vibrating as it moves ?

I’m trying to move ship but it’s not moving smoothly. The ship is vibrating as it moves.

 void MoveShip()
    {

        float yPos = Input.GetAxis("Vertical") * Time.deltaTime * movementSpeed + transform.position.y;
        float zPos = Input.GetAxis("Horizontal") * Time.deltaTime * movementSpeed + transform.position.z;

        transform.position = new Vector3(transform.position.x, yPos, zPos);

        if (movementSpeed <= 15)
        {
            movementSpeed = 15;
        }
    }

This video may help understanding
https://streamable.com/6vrymw

Are you moving the ship in update method? If so try moving it to fixed update.