Cookbook. Skip down to the troubleshooting section. There’s one on diagnosing Pi crashes. And one right below that on accessing your log after ancrash/restart.
You’ll look at power, Disk. And then memory load.
Btw mine started doing this when they did some changes in early 2024. I’m pretty sure I was running into a thread issue or memory exhaustion from a leak. But never chased it down. Moved to a NUC