Depends on the mechanism by which I can't die. Maybe an invisible force stops me from doing dangerous things. Maybe I have just really good luck for four years. Maybe I am literally immortal for four years, like shoot a gun point blank at my cheat and it bounces off the skin.

Potentially start a mega church / cult as the second coming of everyone's god(s). Readjust some beliefs to start from a baseline of every single human being having human rights. Rake in money from the rich fucks who think they can buy their way into some sort of heaven.