Random Speed to an Object Rotation

Hello, I am new to programming and could not find the solution to assigning a random speed to an object rotation. I don't know if it is possible or not.

I have a circle outside of game screen bounds and i want it to rotate in a fixed direction but at random speed which I can modify in the editor.

at the moment i'm using this code -

  public class Spawner_Circle_Rotate : MonoBehaviour
     {
         [SerializeField]
         private float rotSpeed;
         
         void Update()
         {
             transform.Rotate(0, 0, -1 * rotSpeed);
         }
     }