Keep me posted with your problem cause I think I have the same trouble. Hopefully it's covered under warranty.I can't tell from your profile where you're located but if you have a Canadian model, it could be the key chip sensor.
Mine (also 2010) has just started acting up; I'm waiting for it to be consistently bad so the dealer can reproduce the issue and replace the chip sensor. When it fails to validate the chip, the engine cranks but doesn't get fuel and therefore doesn't start. Taking the key out, turning it over and putting it back in usually does the trick - for now.
Of course if you don't have chipped keys, this won't apply to you! =)
That's interesting - though so far turning the key over and restarting quickly has been working for me. Next time it happens, I will try the ON-5s-START routine to see if it makes a difference before repositioning the key. Best to have the knowledge one way or the other before trying to get any work done.@amckie
What you describe is also a possible sign of a slight loss of fuel rail pressure after the vehicle has been sitting. That's why I suggested that the OP wait just a few seconds between "On" and "Start" positions. Even a Santa Fe that's working 'normally' will sometimes balk at starting if the key is inserted and switched quite quickly to the "Start" position.