A little long of a post, so here are the cliffnotes... Perfect running 03 ZHP with 196k started up this morning misfiring on all cylinders, turned off, 30 mins later ran just fine, then ran/runs fine rest of day including 3-4 startups and about 25 miles. I'm confused.

Actual story...

I've owned my 03 ZHP sedan for a couple years now and put about 20k on it. Never had a single issue, engine or otherwise (small things here and there but nothing like this). This morning I started the car and got a bad and odd surprise... First thing I noticed is how quickly it started. There wasn't the usual 2-3 cranks, rather fired right up probably at first crank, within half a second of turning the key past the "on" position. "Too quickly" is best way to describe it. Then I heard some of the usual chatter/rattle of the flywheel (I believe, seems normal as it hasn't gotten worse in 20k, but beyond the point) and didn't think much of it. Usually when I accelerate a bit at idle in neutral the chatter goes away. It did go away, BUT this time the engine kept rattling. It was a light rumble/rattle and seemed like it was simply misfiring on all cylinders (which I later found out was true). Few seconds later, the SES light came on. This all happened in about 15-20 seconds.

I moved the car outside of my shop space (needed to do some work for a client) and parked it outside.

I went to it about 20 minutes later to show my employee how he can go ahead and gloat that BMWs suck because they're unreliable pieces of crap (Lexus owner, which I can respect after owning a few Toyotas, still do ). Started it up and... perfect start with no SES light. Shut it off and had my mechanic (lucky he was in the area with his tools) stop by about 30 mins later. He read the codes and got misfire on all cylinders as well as a code for the oil level sensor.

He started the car and it ran fine, then I drove it a few times throughout the day and also home, so about 25 miles total after the morning "rumble". No issues at all, so I'm obviously puzzled and wanted to share in case someone has any ideas what could've caused that.

Thanks in advance.