Weird No Go Situation

Had a bizarre set of circumstances happen today:

Driving my 2008 Cabrio I pulled up to a place, shifted into neutral, left the car running while I ran a quick errand, came back out and when I tried to shift into reverse, the gear indicator disappeared from the instrument cluster and no shifty. No R, no D, no +/-. Car was running but it never shifted out of neutral.

I figured it jus got discombobulated so I switched it off. When I tried to start it, the dash lit up normally, but no start. No nothing, no click, no low battery sound, nothing. And the P disappeared from the dash.

Tried it several times, no go. I texted my son to see if he could bring me some tools and when I finished, I tried it again and it fired right up, shifted normal.

50 miles later without a problem, probably 8-10 starts, stops, shifting, etc. and it happens again.

Same scenario: Left it running while I ran into a restaurant to pick up a to go order and it won't shift out if neutral and the gear indicator disappears from the cluster. Turn it off, nothing. Lights light, P disappears when I try to start and (IIRC) an alarm akin to the door ajar alarm is going as long as I have the key turned to 2. (I can't say this didn't happen the first time it occurred, but I don't remember it.). This time the check engine light came on.

Once again, after a few minutes it started right up and did so 2 more times until I got home.

So my scan tool is down at my storage unit so I won't be able to scan the MIL until tommorrow, but in the meantime, any suggestions?


And to further confuse the issue, here's some data that probably has nothing to do with the issue, but who knows:

I changed my trans fluid two weeks ago. I bought 3qts of fluid but I used what I thought was about a 1/2 pint to clean and flush my ATF pump. It was a very cold day, but I did what I could to warm the fluid up (set the 3 bottles in the sun while I changed my oil). It was slow going, but I finally got to the end of my fluid and it was only BARELY coming back out of the filler hole.
So for two weeks I've been second guessing whether I used WAY more ATF cleaning out my pump than I thought and my trans fluid was low.
So, I bought another few quarts of fluid (I need to change another car's fluid that takes the same stuff) and yesterday (nice 50° day) I intended to "fill" my trans the rest of the way. Well, surprise surprise, when I opened the fill plug about 1/2 pint of warm fluid came OUT! So rather than driving 2 weeks with low fluid, I was driving 2 weeks with it overfilled. Either that or the fluid expanded to the point when warm that 1/2 pint came out and I'm actually running low now. I don't remember anything about this in the Trans Fluid change procedure, so I'm assuming warm or cold, fluid level should be to the bottom of the fill hole.

I'm hoping this explains why my fuel mileage went from a consistent 37-39mpg to 3 tanks at 32-33. Does it have anything to do with the issue I had today? I doubt it but stranger things have happened.