I have issue with two phones on /e/OS which have the same behavior : it turns off alone and can’t be started back normally.
First a Xiaomi Mi 9T with OS version 3.6-a15 davinci. Sometimes it turns off alone without notice and then it can’t be started up again from the power button. I need to launch from fastboot (volume down + power) and then restart the phone to make it start. No root.
Second OnePlus Nord AC2001 with /e/OS 3.7-a16. Exactly same issue, it was the first of my two phones that had this behavior. I thought at first that the battery was dead and I ordered a new one but it seems that it was this same bug. I could start it back by launching to the fastboot mode and then restart. No root either