Thanks for watching.. I am using an Arduino Nano with SIM800L module to send and receive messages and commands are executed correctly.. In the design I am using an external power supply for the Arduino via a battery.. When the battery is disconnected by the switch, the power to the Arduino is disconnected here when I Turning it on again the arduino only works by pressing the restart button.. I want a solution to this problem I want when I unplug the power from the Arduino and then plug it in it executes the code without pressing the restart button every time