exactly same problem today. driving normal conditions for 20 minutes, stopped at car park with wheels turned at angle, turned off engine went shopping.
Came back. no start. "Steering wheel locked". So I had read other forums about easing pressure on the column so I straightened wheels and ensured no undue pressure was being applied by wheel angle. still no go. waited 10 minutes no go. disconnected power waited 10 mins.no go. even tried "lock / unlock 4 times to reset the security" as advised by roadside assist phone operator (as if) .
So I'm keen to see how others solved this. I cant find a manual for a 2007 SE6 anywhere.
I suspect it is a faulty sensor as the steering actually turns if forced. Not a single salesman knew of the problem or a solution, but they know how to sell a car and take a commission, right ?