It could be a number of things. The fact that the check engine light came on makes one wonder if this is something more serious vs. an ignition switch failing. When ignition switches go, it usually happens at startup and windows don't work or the AC controls are absent or the wipers won't work (general description of a demon-possessed boxster).
I think you need to have it diagnosed properly by a dealership or an experience Porsche mechanic.
I hope its something small, but from the way you've described it, it smells a lot worse than a sensor or a switch. I do hope I am wrong though
Did the check engine light come on and stay on, or did it blink?
Blinking means, "pull over and shut off the engine, you are screwed."
Just turned on and staying on means, "get it looked at, there's something small that needs to be replaced" <-- small doesn't mean inexpensive though, especially if its emissions-related.