Glad to hear things are at least somewhat back to normal.

I'm not a locksmith, or a pro mechanic. But it seems to me that either wear in the lock cylinder, wear in the key, or (very likely) the twist in the key, perhaps a combination of those factors, is causing the pins in the cylinder to not fully engage. This is permitting the lock to turn, but with much friction. The sound you heard after starting was the starter motor pinion failing to disengage with the ring gear on the flexplate. This occurred since the friction in the ignition cylinder was greater than what the return spring could overcome.

The issue seems better now, but I suspect it will return. Trying to straighten the key would be my first step. It should be brass, a very malleable material that should straighten easily. A bench vise with brass jaw inserts would be the ideal tool to hold the key while you twist it back, but you can improvise. If the key looks worn, maybe just have another made. Not a copy of that, but a new one by someone who can do it from the code (dealer). Do you happen to have a spare - even the service / valet key, to compare?

Good thought on the ambient temp, but living in New England all my life, much of that with older cars, has never presented this issue with an ignition key. Door locks, sure. The tailgate latch on my 945 is frozen as I type this. There are lock lubricants, which I use, but I wouldn't do it for the ignition unless out of the column, for fear the stuff might make its way into the switch located at the end of that cylinder.

Hope this can help - Wilson.