Why does my car just shut off and won’t crank ?

I have an2008 Mazda 6 and it keeps just
turning off on me . I’ve took it to the shoot
they checked my alternator I got a new
battery and starter it was none of the above !!!
It just shuts off can’t and won’t crank no lights
come on can’t turn on hazards lights or
anything . Nothing works like the car just
completely dies . What could it possibly be ? I
don’t wanna keep spending money I don’t
have taking it to different shops !! I was door
dashing with my one year old when this
happened and I’m not sure what it is or could
be ..