Happens to me during winter, I tried cleaning my terminals and tighten the bolts on it (battery). Later i removed the starter alarm relay. it was sticking....
When it would happen to me I just took the key back out, opened the door. closed it. start again. DO not know why but it seemed to start.
SVX ghost?
Try this: have your car running, remove both connections to battery. if it dies. it might indicate to alternator isues. Please do not touch both terminals or hold them uninsulated. 12dc is a lot