First read this.
It’s hard to help you this way - what does that mean lagging? It loses frames? It teleports? Stops movement sometimes?
I do not know what asset you use, but if you can’t make smooth camera movement or whatever the problem is, then it would mean it’s bad asset - most likely you just did something wrong.
If you want to be sure, that camera doesn’t jitter it must be updated every frame. It means you must do it in Update or LateUpdate. If your car uses rigidbody (mostlikely true) then it need to be updated in FixedUpdate, so it’s synchronized with physics. Possibly it’s not about the camera, but AI itself.
With such little information, that is all I can personally say.