I know that pikuach nefesh, saving a life, can push off Shabbat (which I understand to mean, can excuse breaking rules on Shabbat). If I am one of a group of Jews who could do the life saving, should I volunteer to be the one who will have to break Shabbat or should I either let someone else volunteer (because my participation is not a sine qua non) or let the situation develop until I am the only choice?
And what if waiting for anyone else volunteer, or letting the situation develop might then preclude any life saving -- should I jump at the role before I am the only choice because the opportunity is inherently important, or not, because one should not put oneself in the situation which then has to be excused via invoking pikuach nefesh?