if (centerval == 0)
{
  myservo.write(90);
}
else if (leftval == 0)
{
  myservo.write(60);
}
else if (rightval == 0)
{
  myservo.write(120);
}
else {
  delay(1000);  // or however long you need to delay
  digitalwrite(motorpin, LOW);
}