First Person Camera is extremely jerky

Must be something in your system, because there's nothing jerky about it here or on any other computer I've used. Putting a first-person camera script in FixedUpdate is not the right thing to do...that will make it only update when the physics system updates, instead of every frame. Try turning off any mouse hacks or utilities you might be using.

maybe its the computer thats running a bit slow?

Searching the forums I found the following script and it solved my FPS camera movement (I’ve made some adaptations to the original script to fit my needs. Sorry, I don't know who the author is).

     using UnityEngine;
 
 using System.Collections;
 
 using System.Collections.Generic;
 
 
 
 public class SmoothMouseLook : MonoBehaviour
 
 {
 
     /*
 
     This script is used to average the mouse input over x 
 
     amount of frames in order to create a smooth mouselook.
 
     */
 
 
 
     //Mouse look sensitivity
 
     public float sensitivityX = 2f;
 
     public float sensitivityY = 2f;
 
 
 
     //Default mouse sensitivity
 
     public float defaultSensX = 2f;
 
     public float defaultSensY = 2f;
 
 
 
     //Minimum angle you can look up
 
     public float minimumY = -60f;
 
     public float maximumY = 60f;
 
     
 
     //Number of frames to be averaged, used for smoothing mouselook
 
     public int frameCounterX = 35;
 
     public int frameCounterY = 35;
 
     
 
     //Mouse rotation input
 
     private float rotationX = 0f;
 
     private float rotationY = 0f;
 
     
 
     //Used to calculate the rotation of this object
 
     private Quaternion xQuaternion;
 
     private Quaternion yQuaternion;
 
     private Quaternion originalRotation;
 
 
 
     //Array of rotations to be averaged
 
     private List<float> rotArrayX = new List<float> ();
 
     private List<float> rotArrayY = new List<float> ();
 
 
 
     void Start ()
 
     {
 
         //Lock/Hide cursor
 
         Screen.lockCursor = true;
 
         
 
         if (rigidbody)
 
             rigidbody.freezeRotation = true;
 
         
 
         originalRotation = transform.localRotation;
 
     }
 
 
 
     void Update ()
 
     {
 
         if (Screen.lockCursor) {
 
             //Mouse/Camera Movement Smoothing:    
 
             //Average rotationX for smooth mouselook
 
             float rotAverageX = 0f;
 
             rotationX += Input.GetAxis ("Mouse X") * sensitivityX;
 
             
 
             //Add the current rotation to the array, at the last position
 
             rotArrayX.Add (rotationX);
 
             
 
             //Reached max number of steps?  Remove the oldest rotation from the array
 
             if (rotArrayX.Count >= frameCounterX) {
 
                 rotArrayX.RemoveAt (0);
 
             }
 
             
 
             //Add all of these rotations together
 
             for (int i_counterX = 0; i_counterX < rotArrayX.Count; i_counterX++) {
 
                 //Loop through the array
 
                 rotAverageX += rotArrayX[i_counterX];
 
             }
 
             
 
             //Now divide by the number of rotations by the number of elements to get the average
 
             rotAverageX /= rotArrayX.Count;
 
             
 
             //Average rotationY, same process as above
 
             float rotAverageY = 0;
 
             rotationY += Input.GetAxis ("Mouse Y") * sensitivityY;
 
             rotationY = ClampAngle (rotationY, minimumY, maximumY);
 
             rotArrayY.Add (rotationY);
 
             
 
             if (rotArrayY.Count >= frameCounterY) {
 
                 rotArrayY.RemoveAt (0);
 
             }
 
             
 
             for (int i_counterY = 0; i_counterY < rotArrayY.Count; i_counterY++) {
 
                 rotAverageY += rotArrayY[i_counterY];
 
             }
 
             
 
             rotAverageY /= rotArrayY.Count;
 
             
 
             //Apply and rotate this object
 
             xQuaternion = Quaternion.AngleAxis (rotAverageX, Vector3.up);
 
             yQuaternion = Quaternion.AngleAxis (rotAverageY, Vector3.left);
 
             transform.localRotation = originalRotation * xQuaternion * yQuaternion;
 
         }
 
     }
 
 
 
     private float ClampAngle (float angle, float min, float max)
 
     {
 
         if (angle < -360f)
 
             angle += 360f;
 
         if (angle > 360f)
 
             angle -= 360f;
 
         
 
         return Mathf.Clamp (angle, min, max);
 
     }
     }

Steps to use it: Add a First Person Controller to the scene and remove the Mouse Look script all together 1) Attach Smooth Mouse Look to the Character Controller with this parameters:

Sensitivity X: 4 Sensitivity Y: 0 Default Sens X: 4 Default Sens Y: 0 Minimum Y: 0 Maximum Y: 0 Frame Counter X: 20 Frame Counter Y: 20

2) Attach another Smooth Mouse Look to the Main Camera with this parameters:

Sensitivity X: 0 Sensitivity Y: 5 Default Sens X: 0 Default Sens Y: 5 Minimum Y: -60 Maximum Y: 60 Frame Counter X: 20 Frame Counter Y: 20

That’s it!

I have the exact same problem as the person wrote above. I once had Unity on an old machine and it was a bit jumpy then. I now have a Core i3 computer with Intel HD graphics and it is very jerky. I have gone through all the graphics settings but it hasn't changed anything.