My 2011 Edge had the exact same symptoms, but this would only happen after filling up. I would turn the key and hear it crank for about 5 seconds then usually (99.9% of the time) turn over fine. Every once in a while, it wouldn't start. I'd turn the key off and try again and the Edge would start normally.
I replaced the purge palve this week, but haven't gotten gas yet to see if the issue is fixed. I'll provide an update if this is resolved.