Getting a player's position to move on contact with a plane

I’m super new to unity and I’m taking an intro class. I’m trying to figure out how to get my player object to move back to starting point after coming into contact with a plane which is set directly below the play area. So far I got this

void OnTriggerEnter(Collider collider)
{
    if (collider.gameObject.name == "Player")
    {
        
    }
}

You need to pass the start position to the script and then

collider.gameObject.transform.position = startPosition

But if the plane is directly below the play area means that there is a y value which the player shouldm usually be able to get to so I would rather do something like this in the player controller:

if(this.transform.position.y < yourMinYValue) {
    this.transform.position = startPosition;
}