how to calculate the initial position

hello, I am currently working on a racing game; I would like that when the car is off or when there is a crash the vehicle will resume its original position. I would like to know if there are functions capable of doing its in unity.......

 

That question is very broad, and the description is very vague. Define what's the "initial" and/or "original" position for you in that context / in your application.

Yes, of course it's possible.
It's just that you have to define the behaviour first, then implement it using various API calls so that you achieve the desired behaviour.

 

If what you mean by "original position" is literally the place it was when the race started, you could achieve that by:
1) Placing a a collider somewhere under the track that detects in case the player left it
2) Create an empty object where the "original position" is
3) Get the transform.position.x, y and z of that empty game object and apply it to car

Colliders are easy to use, and to set the position you can follow the idea from the next tutorial:

https://docs.unity3d.com/ScriptReference/Transform-position.html

I think that pretty much covers it!