My 06 Altima actually stalled out on me while I was doing 50mph. It lost all engine power, but my radio & headlights were still on. I coasted to the nearest side road & put in park, turned the ignition off & waited a few minutes, then tried to restart it. Nothing. No crank, no clicking, no start. But my battery ( hence my alternator) was working just fine. So I had it towed to my home & began troubleshooting. After verifying that the battery, starter, alternator, fuel system, fuses & all wiring were all in good working order, I also made sure that the Cam, Crank & O2 sensors were good. After checking all of this, I still had no clue why my car suddenly died in transit & wouldn't restart. At my wits end, I made a last ditch effort at DIY diagnostics & began searching terms & keywords on Google. After reading 999 pages that were not helpful, I finally found a page that explained something that I hadn't even considered, much less tried. The ignition relay (switch) inside the fuse box under the hood. Upon determining that it was indeed ‘bad', I hurried to the nearest auto parts place, bought a new one, and immediately replaced it. And VOILA….my car started on the first try!! !