Waiting for USB Serial

Are you using this with your Serial.begin command on an Arduino with USB serial?

  Serial.begin(115200);
  while(!Serial)
    ;

We found on the MKR GSM 1400 and Arduino Micro this would cause the program to not run if the Arduino serial monitor was not open! Doing this fixed it:

  Serial.begin(115200);
  //while(!Serial)          //Don't do this or we won't start if the Aruino IDE Serial Monitor is not turned on!
  //  ;