For about a week, now, my car's been having sporadic issues with rough idling. It's not consistent at all, though it seems to happen more often when the car is warm than cold. Most of the time, it'll be running fine, then I'll hear a click, and the idle gets rough. Three times, now, the car has turned on, and the RPMs have dropped straight back down to 0, and the car died. If this happens when I turn the car on, I can hold my foot on the gas constantly for the first few minutes (just keeping it at 500rpm or higher) and I'm fine.

I did have a similar problem in the past, though worse, and most specifically when the car was cold. A tune up fixed it.

Someone already suggested that it could be either A/C or defrost. It's winter, so it's not the A/C, and I tried running with my heat off entirely -- or as entirely off as it can go in a 740 -- and it did no good. All fluids are fine, nothing looks wrong in the engine (though it's tough to check that myself, as when the car is in dying mode, I can't very well get out and see for myself, and when I've had other people around to look, it's been too cooperative with the idea of running well).