I have a simple launchd plist file that I am using to run a shell script that is designed to restart the computer:
<?xml vesion="1.0" encoding="UTF-8"?>
<!DOCTYPE plist Public "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
echo <password> | sudo -S shutdown -r now
launchctl load com.sag95.restartscript.plist
launchctl load only loads it for the current session. Next time you log in, it loads your list of launch agents from /System/Library/LaunchAgents/.plist, /Library/LaunchAgents/.plist, and /Users/sag95/Library/LaunchAgents/*.plist. If the file isn't in one of these folders, it will not get loaded.
Assuming you want it to run only when you are logged in, place the file in /Users/sag95/Library/LaunchAgents. If you wanted it to run for any logged in user, put it in /Library/LaunchAgents instead (but with this specific script, the password will only work for your account, so this wouldn't be useful).