How old is the battery. I had a gen 2 3.0 in the past that was doing the same thing. The battery was an older Optima at the time. It turns out the cranking amps had dropped over the years. Once I got a new battery the problem went away.

Another thing to check; how clean or corroded are all the connections? Not just at the battery but also at the termination of the ground wires.

I just want to tell you both good luck, and we're all counting on you.