No warning whatsoever. The only thing that precedes the shutdown is a sudden misfiring/rough-running for about 1-2 seconds. I've been able to temporarily keep it running for another 15 seconds by nailing the gas pedal, but it's only for that brief time period.

No "check engine" light ahead of time. No hesitation or prolonged rough running. Engine restarts immediately upon shifting to Neutral and twisting the key. Usually it will continue running normally after the restart for the next 15-20 miles (I'm usually where I need to be before then). It always starts immediately after being parked for any length of time, and there is absolutely no battery weakness at any time.

What confuses me, the disconnecting of the battery stopped the problem for 10 days. NO PROBLEM AT ALL!! So, the reset of the electronics/computer programs apparently solved the problem. What appears to have happened is the "virus" has re-invaded the computer and here we go again.

There is nothing to indicate alternator problems, and the Service Manager at the Subaru dealership in Jacksonville told me it was almost impossible to lay the blame at the feet of the alternator.
This by phone, as I don't want to drive for almost an hour in heavy traffic to get there in person... not if I don't have to