ford focus, starts drives but when idle or in park it shuts off!?

[Robert]

I am having some problems with my ford focus it starts right up it drives but after a while when i pull up to a stop light it sound like it wants to shut off and when i get to where i'm going and put it in park it shuts off, it seems like it will stay on when its in gear but not when its in neutral or park. help please!!!