Choch votes for RCM solder failure. And that IS a possible culprit.

BUt I vote for Crank Sensor. Mine failed just like yours, at a stoplight. Had to try three time, it started.
I read the OBD, had a code for crank sensor. Changed it and drover the car almost another year with no more trouble.

See, the thing is, the crank sensor usually throws a code and turns on the Check Engine light.
BUT, it does not ALWAYS throw a code.

DO NOT buy one at Autozone, etc. Go to Needswing.com, GermanAutoSupply.com, etc.
I'd also have the solder on the RCM re-flowed.