No Start. Then Start 5 Min Later.
 

Boxster driving is fun.

Your problem sounds like a simple -bad- main ground or power connection.
I would look at the battery connections first.
Battery ground cable connection at the chassis second.
Also there is a ground connection near the power steering reservoir that can come loose.
If you do a search here on the forum you should be able to find a picture of it.
This is where I would start.
Simplest things first.

I've had a no crank/no start in a Boxster with a Tiptronic transmission that was not quite fully in the Park position. It could happen in a manual transmission car if the clutch pedal safety switch is stuck.

Old thread: http://986forum.com/forums/performance-technical-chat/22842-need-help-intermittent-starting-problem.html

I took it when he said he "turned the key and got absolutely nothing" that he meant no power to anything.
If it was a no crank/no start I would approach the problem a little differently then I outlined above.

Boxster driving is fun.

Well with that info:
Do the checks I mentioned previously.
Check the condition of the clutch safety switch. As mentioned by 78F350
Go on youtube and find a video on how to do a voltage drop test on your starter system.
A Relatively simple test but a visual of it will do better then I can describe it.
A voltage drop test on the starter system will tell you if you have any problems or potential problems with the starter or its related wiring.

If it happens again, note if the tach needle twitches at all.

Crank position sensor . Almost 100% sure. My guy charged 280 for the part

steering wheel lock?
 

I've experienced a problem where i have power but nothing happens when I turn the key. Turning the steering wheel released it and car started.

Probably not your issue but it is one thing to check for anybody searching this problem.