Well I have a doozy of a problem with my Optima it all started last week with it dieing while pulling out of the driveway. it did restart half hour later and all was good until a couple days ago I was pulling out of a parking lot and it just died again, I did get it to restart but the car ran very poorly very rough so I shut it down. At the moment its sitting at my buddys shop with multiple can bus codes. He did get it to restart it ran for awhile it ran smoothly and then shut down on its own and now will not restart. The only thing he has come up with at the moment is that there is no fuel (fuel pump checked and is good) and a little gas down the intake and the engine starts. I do have a viper auto start installed and has been for years without an issue (I use it) but he's thinking it's the issue I do not..but who am i to say I was a former mechanic he still is and is up to date where i am not. If anyone has seen this issue or can offer some suggestions please feel free to post here id appreciate it.
I just went through a similar situation in the past month with my 2012 Kia Optima SX-T, my engine seized on the interstate at 70mph, it would not restart and then the engine immobilizer symbol (car image with key lock on it) came on the dash display at the top, my car had 127k miles on it. There is a thread on here that I posted if you care to look it up.
Long story short, Kia replaced my engine with a brand new 2021 Turbo, also the starter and fuel injector wiring plus the computer was upgraded to work with the brand new 2021 Turbo engine AT NO COST TO ME under the engine recall Kia & NHTSA have out there for the 2012's. I HIGHLY SUGGEST you call Kia directly and open an engine failure case like I did, you will have to bring or tow your car to a Kia Dealership to have the engine diagnosis done, chances are they will replace it just like they did mine. I had all sorts of strange things start happening before the engine seized while driving, everything from it not starting, to running real rough, waste gate suddenly froze up, to the back up camera suddenly not working. In hindsight I think these were all warning signs that something bad was about to go wrong with the car that I wasn't aware of. I was aware of the recall on the engines and mine had not been replaced yet so it was only a matter of time before it would seize. CALL KIA, open a case and get your car to a close by authorized Kia Dealership for the diagnosis. Hope this all works out for you as it did for me, I really threw a fuss about the engine seizing with the 2012 as I also own a 06.5 Kia Optima XLS with 260k on it and that car runs like brand new and has given me hardly any issues over the last 14 years from the day I bought it brand new. Call Kia Customer Service right away and get the case opened on the engine recall for the 2012's