Yeah, like others have said... I probably would. Both because of SI and human instinct to move in those sorts of situations, and also because a car accident is not a clean or guaranteed death. But I do think if I was getting mugged and someone had a gun pointed to my head or something, I would gladly let them.
If someone was mugging me with a gun to my head, I would straight up tell them that they're going to need to pull the trigger and potentially take a murder charge if they want anything from me.
And I would pray that they pulled the damn trigger.
But, with my luck, they'd probably be using a cheap gun, and cheap ammo, and I'd end up a damn vegetable or otherwise still be capable of breathing.
Can't really depend on a mugger to properly hit the brainstem.
I think they're probably expecting you to just give up whatever you have of value, and not expecting to actually have to shoot you- and if they have to, they likely won't be putting any thought into whether or not their shot placement is correct to cause death.