91 420SEL working well until 2 days ago.

Started cold in morning and when I shifted to reverse, engine stalled. Did not think much of it as re-started with ease.

Drove 40+ miles on freeway. Stopped at bottom of ramp and all was well. Travelled approx 1/4 mile and then had to make sweeping rt turn and engine stalled. All warning lights on including low fuel light. Stopped, put trans in park, and restarted with ease.

All was good until today (2 days later). Travelled on cold engine for approx 10 miles in stop/go traffic. Stopped for about 1.5 hrs and upon restart, all warning lights on and cooling fans running at high speed. I turned off and immediately re-started and all appeared normal again.

Anyone seen this before?

Any suggestions?

Thanks