What's causing my Rx8 to not start?

My rx8 started to die on me recently everytime I would stop at a red
light. I took it to a mechanic and told me it was the crankshaft sensor so
I had that replaced. It drove fine during the day but at night it have out
on me again. It wouldn't start. Only until 5 min later it would. I let my car
sit for a couple a days without starting it and now it won't start
completely. It would crank but not start. The dashboard light dim on and
off. And some icons would flicker. What could be the problem?