@juiceme
Reason might be not clear, but random shutdowns and reboots are definitely a common issue with Jolla. You can see many users affected here: https://together.jolla.com/question/...ly-shuts-down/
And Jolla team is aware that this is plaguing the device, some fixes pushed already in coming release.
All started for me after 1.0.3.8, until then it was pretty much fine. Lets wait and see what comes next For me resetting is the final option, you better try to find the culprit because if you had it once, most probably it will appear again.