Suddenly Unsmooth Rotation Animation ?HLEP!!!

Animation
1

I’m a fresh beginner.Anyone can help me?

I am making a Cart Game .I want Record my car’s trace.And play the replay.
My idea is :
1:record the car’s position and eulerangle every 5 frames.(about 10 keyframes per second)
2:make the keyframes be curves.(And Question Comes)
Unity Animation cannot save the eulerAngles component.So I had to convert it into Rotation:
Quaternion q=Quaternion.Euler(rot);
then get q.x,q.y,q.z,q.w
3:Set position curves and rotation curves to animation:
animTemp.SetCurve(“”,typeof(Transform),“localPosition.x”,curves[0]);
animTemp.SetCurve(“”,typeof(Transform),“localPosition.y”,curves[1]);
animTemp.SetCurve(“”,typeof(Transform),“localPosition.z”,curves[2]);
animTemp.SetCurve(“”,typeof(Transform),“localRotation.x”,curves[3]);
animTemp.SetCurve(“”,typeof(Transform),“localRotation.y”,curves[4]);
animTemp.SetCurve(“”,typeof(Transform),“localRotation.z”,curves[5]);
animTemp.SetCurve(“”,typeof(Transform),“localRotation.w”,curves[6]);
4:Play the animation

but the rotation animation shape is not smooth:

my animation can be played but it is always shake.
Thanks for anyone who would help me.

2

If i drag any keyframe’s tangent handle of animation curve,all curve become good.I don’t know why.Of course ,I can’t do this after publish.

3

Well,I have conquer the problem.
before convert to quaternion,I do the function:
while(rot.x>180){
rot.x-=360;
}
while(rot.z>180){
rot.z-=360;
}