Take a look at the code - there should have been a total of THREE 10-second pauses... no?
No. But this will help...
void setup() {
unsigned long start;
...
Serial.println("First loop");
start = millis(); // <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
while(1) {
...
Serial.println("Second loop");
cmd_response = "";
Serial3.println("AT+CWMODE=1");
start = millis(); // <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
while(1) {
...
Serial3.print("\"\r\n");
start = millis(); // <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
while(1) {
...