It did this a few months ago, and I brought it in for the service guys to check that out. They found some trouble codes in the computer, calibrated something, and sent me on my way.
Roughly a month ago, it started doing it again. Once a week, it would lapse into that behavior, and a few minutes to a few hours later it would be working again. Yesterday, it happened twice (first thing in the morning, and after I stopped by the UPS Store), so I brought it in again this morning.
The first thing that the service desk person did was to ask about keeping the car here for the day, to see if they could get it to not start like I've seen it do. That, of course, didn't work for me... I knew the problem was intermittent, and as a software developer I know how unreliable problems like that can be when trying to get them to happen on command. Forensic evidence, when you can get it, is much more reliable. For that reason, I asked them to start by checking the car's computer for any trouble codes that it might have stored, and I'd hang around tentatively. They found one, and are currently waiting on a return call from some central Ford office concerning what to do about it.
In the meantime, I'm working from their customer lounge... I'm thankful in all kinds of ways for having the option of working outside the office as needed, and this Ford dealer having free WiFi access for customers.
They just got a call back, with a lot of stuff to check out. Another thing to be thankful for? The extended service plan I got when I bought the thing... the rental I'll be needing is covered.