Hello! Welcome to PS5Forum.com!
I'm sorry for no answers, most of the time when there isn't an answer, it's because there isn't many players with a particular answer or experience.
For example, I'm the owner of the site, but don't have one. It's hard to find one.
However, if your console is unexpectedly shutting down, it's probably because it's either a hardware defect or a software issue. Most of the time, when there's a software issue, it can easily be fixed in a patch update. Either call Sony, or use the PlayStation.com website. All the information is enclosed in a instruction manual that came with the console.
I have questions though, what did you do before you shut down the console, or what? Where is your console located in the house? The reason why I ask is because it needs enough circulation from outside in order to keep the console cool. Here's a video that may help...