Stop led from blinking when running I don't get it. I'm new to Arduino, but not to programming. I don't understand why led pin 13 keeps blinking. 

here is my code..

#include &lt;Servo.h&gt;

// X servo angle will stay in [min_x, max_x] range
// Y servo angle will stay in [min_y, max_y] range
// to be adjusted to the size of your living room

float min_x = 5;
float max_x = 50;
float min_y = 5;
float max_y = 35;
int min_freeze = 200;
int max_freeze = 3000;
float minimal_movement = 5;

// finding center of square for starting point
int random_delay;
float x_position = min_x + (max_x - min_x)/2;
float y_position = min_y + (max_y - min_y)/2; 
float x_old_position = x_position;
float y_old_position = y_position;
float x_new_position;
float y_new_position;
float x_speed;
float y_speed;
int movement_time;

// Instantiating two servos
Servo x_servo;  
Servo y_servo;
int pos = 0;

void setup() {
  y_servo.attach(6);  // attaches the y servo on pin 6 to the servo object
  x_servo.attach(9);  // attaches the x servo on pin 9 to the servo object
  pinMode (13, OUTPUT);
  digitalWrite (13, HIGH);  // switch on  the laser

  //Place the servos in the center at the beginning 
  y_servo.write(y_position); 
  x_servo.write(x_position);     

}

void loop() {
  movement_time = random(10,40);
  random_delay = random(min_freeze, max_freeze);
  x_new_position = random(min_x+minimal_movement, max_x-minimal_movement);
  y_new_position = random(min_y+minimal_movement, max_y-minimal_movement);

  if( (y_new_position &gt; y_old_position) &amp;&amp; (abs(y_new_position - y_old_position) &lt; 5 )) {
    y_new_position = y_new_position + minimal_movement;
  }  else if ( (y_new_position &lt; y_old_position) &amp;&amp; (abs(y_new_position - y_old_position) &lt; 5 )) {
    y_new_position = y_new_position - minimal_movement;
  }

  if( (x_new_position &gt; x_old_position) &amp;&amp; (abs(x_new_position - x_old_position) &lt; 5 )) {
    x_new_position = x_new_position + minimal_movement;
  }  else if ( (x_new_position &lt; x_old_position) &amp;&amp; (abs(x_new_position - x_old_position) &lt; 5 )) {
    x_new_position = x_new_position - minimal_movement;
  }

  x_speed = (x_new_position - x_old_position)/movement_time;
  y_speed = (y_new_position - y_old_position)/movement_time;  
  for (pos = 0; pos &lt; movement_time; pos += 1) { 
      x_position = x_position + x_speed;
      y_position = y_position + y_speed;
      x_servo.write(x_position);  
      y_servo.write(y_position);                    
    delay(10); 
  }
  x_old_position = x_new_position;
  y_old_position = y_new_position;
  delay(random_delay);

}


Nowhere in this sketch, the line "digitalWrite (13, LOW);" is contained, yet I am unable to keep the LED on solid without blinking when the Arduino is looping. I've other people do it, with this code, I don't get what I'm missing!

Windows 7 64bit, Arduino Uno board, Arduino 1.8.9 program
I tried your sketch on an Arduino Uno, with no servos connected, and the LED on pin 13 did not blink.

DataFiddler makes a good point in their comment. To be sure you are actually uploading the sketch, try uploading the Blink sketch that comes with the IDE. Change the delays from 1000ms to 200ms then upload it. The difference in flash rates should confirm or deny the ability to successful upload sketches.

You don't say which servos you are using, so I'll assume they are SG90. I'm not sure if the data sheet for every SG90 servo is the same, but if you look at this one, SG90 Specifications, you'll see the "stall current" can be between 570mA and 730mA, each. If you are powering them from the Uno, it can't supply that much current. Another limiting factor is the computer's USB maximum current output, (if you are powering the Uno with a USB port). FWIW, my computer can only provide 500mA per USB.

I would suggest powering the servos with a separate power supply, then see what happens.