Great running 300E car just shuts off!!!

[sptt]

I'm driving my finally fine-tuned (what I think is fine-tuned) 300e down a busy street and I come to a stoplight and it just dies! All warning lights come on. I put it in park, start it back up first crank and no problem, and it hasn't happened again all day. Anything I should check? It was idiling soooo nice before and after it happened which is great I think! Some bad gas going through? Should I check plugs? OVP is new. Scared the heck out of me!