1991 944 turbo 185K miles. Generally good tune.

This is the first time ive encountered this happening, and am wondering what might possibly be the culprit. I was driving my car as normal, maybe 25 mph and it simply just died. No shudder, no wierd idle, it just was if i turned the car off while driving. All the lights on the dash lit up. I pulled over, and it started up just fine. No check engine light came on, although the bulb out light did. How can i go about diagnosing this? Is it possible this was a one time fluke, or something worth investigating?