'98 Legacy auto tran shuts off in traffic..will start after 5 minutes.

All of a sudden it's just like you turn the key off and when you try to restart it...there is nothing.  
1)After several minutes it sounds (with key in ign/off)) like a relay contact makes or breaks then the car will start when you turn the key.    
2)When this first happened I was luckily within a block of a Advance Auto and after getting frustrated took the battery in to check it out. The counter guy ran a test and confirmed the battery was strong.
3)The headlights are also strong and don't brighten and dim when the engine is reved up.
4)While waiting for the hook the car ran well for 45 minutes just sitting there.  A couple of times I pushed in the button on the shifter and I could hear the making or breaking of a relay.  The car did stay running and didn't shutter.  Thanks for and help/insight...Bill