IsPointInArea(Float: x, Float: y, Float: z, Float: min_x, Float: min_y, Float: min_z, Float: max_x, Float: max_y, Float: max_z) {
  return x > min_x && y > min_y && z > min_z && x < max_x && y < max_y && z < max_z;
}

new gRespawnTimer[MAX_PLAYERS] = {-1, ...};
new bool: gPlayerInZone[MAX_PLAYERS char];

public OnPlayerUpdate(playerid) {
  new Float: x, Float: y, Float: z;

  GetPlayerPos(playerid, x, y, z);

  if (IsPointInArea(x, y, z, ...)) {
    gPlayerInZone{playerid} = true;

    if (!gRespawnTimer[playerid] != -1) {
      if (IsPlayerInAnyVehicle(playerid)) {
        gRespawnTimer[playerid] = SetTimerEx("Respawn", 4000, false, "i", playerid);
      }
    }
  } else {
    gPlayerInZone{playerid} = false;
  }
  return 1;
}

forward Respawn(playerid);
public Respawn(playerid) {
  gRespawnTimer[playerid] = -1;

  if (!gPlayerInZone{playerid}) {
    return;
  }

  if (!IsPlayerInAnyVehicle(playerid)) {
    return;
  }

  SetVehicleToRespawn(GetPlayerVehicleID(playerid));
}