So I do a traffic stop,  approach the vehicle and driver pulls a gun and shoots me  maybe once or twice and I switch back to Franklin or Michael and the game resets to me at the hospital as whatever character I was at the time.  No script crashes how do I stop this? 

You don't as far as I know, other than just changing your model back using a trainer, or using a trainer to set godmode so you can't die.
Also, it's nothing anybody can fix, keeping a cop model makes the game then load forever.