This is from a demo made from Blink, for simplicity, but my more complex sketch suffers the same problem. I'm running Arduino IDE 2.3.2 with M5Stack 2.1.1, building for M5Stack-Timer-Cam.

Here's the demo code:

void setup() {
// initialize digital pin LED_BUILTIN as an output.
pinMode(LED_BUILTIN, OUTPUT);

Serial.begin(9600);

Serial.println("Starting 1");

while (!Serial) {
; // wait for serial port to connect. Needed for native USB
}

Serial.println("Starting 2");

delay(1000);

Serial.println("Starting 3");

}

// the loop function runs over and over again forever
void loop() {
digitalWrite(LED_BUILTIN, HIGH); // turn the LED on (HIGH is the voltage level)
delay(1000); // wait for a second
digitalWrite(LED_BUILTIN, LOW); // turn the LED off by making the voltage LOW
delay(1000);
Serial.println("loop"); // wait for a second
}