Gyroscope controller jittering when holding phone still

I have here a simplified version of my gyro-controlled camera with a sensitivity modification (a side effect of increasing sensitivity is that the jitteriness is exacerbated). public class GyroControl : MonoBehaviour {

     private Transform _rawGyroRotation;
     Vector3 gyroAdjust;
     [SerializeField] private float _smoothing = 0.1f;
 
     void Start()
     {
         Input.gyro.enabled = true;
         Application.targetFrameRate = 60;
 
         _rawGyroRotation = new GameObject("GyroRaw").transform;
         _rawGyroRotation.position = transform.position;
         _rawGyroRotation.rotation = transform.rotation;
 
     }
 
     private void Update()
     {
         _rawGyroRotation.rotation = Input.gyro.attitude;
 
         gyroAdjust = _rawGyroRotation.rotation.eulerAngles * 2; //increase rotation sensitivity
         transform.rotation = Quaternion.Euler(gyroAdjust);
 
         transform.rotation = Quaternion.Slerp(transform.rotation, _rawGyroRotation.rotation, _smoothing);
 
     }
 }

When in motion, the jittering isn't noticeable. But when you hold the phone still, there's what I assume to be just analogue noise that causes jittering. I would really appreciate any help or advice on how to add a filter or something to reduce the jittering for this kind of controller.

Thanks.