Arduino continuously reading ADC value using interrupt
reset the resultNumber to 0 after you have written it to serial. and turn interrupts back on

void loop () {

  while (resultNumber &lt; MAX_RESULTS)
    { }

  for (int i = 0; i &lt; MAX_RESULTS; i++)
  {
    Serial.println (results [i]);
  }
  resultNumber = 0; 
  ADCSRA =  bit (ADEN) | bit (ADIE) | bit (ADIF)| bit (ADPS2) | bit (ADATE);   
   // turn ADC back on
}