Restart WiFi in Raspberry PI when connection drops

restart_wifi.sh

create a new file /usr/local/bin/restart_wifi.sh
and put below script in it.

ping -c4 192.168.1.1 > /dev/null
 
if [ $? != 0 ] 
then
  echo "No network connection, restarting wlan0"
  sudo systemctl daemon-reload
  sleep 5
  sudo systemctl restart dhcpcd
fi

then

Now make it executable:
sudo chmod 775 /usr/local/bin/restart_wifi.sh

Then add it to a crontab

*/5 * * * * /usr/bin/sudo -H /usr/local/bin/restart_wifi.sh >> /dev/null 2>&1

This command will check every 5 minute if wifi is stopped or not.