arms akimbo? chuck?
first off, do you have a turbo Legacy? or is it non turbo? (hoodscoop / no hoodscoop). also, is this your first winter with the car?
there are some threads around with people that have the same issue as you. I used to have the problem (car stalls completely when coming to stop right after starting it up and it's cold out) but it hasn't showed up this year. I think I may have had an intake leak when the issue was happening to me.
If you can find those threads that this was discussed in, there were a number of solutions people tried. Some worked for some people, but not for others. This is definitely a real problem, though, and Subaru has denied it to everyone who tried to take it to the dealer.