I've been facing this issue for the past few days where Fedora logs out automatically and unexpectedly. There is no common pattern to this, it happens very randomly .. irrespective of applications that are open.
I thought it was temperature related at first because the CPU temperature was kind of high (~75 C) but then it happened again when the laptop was almost idle and the temperature was around 45 C . So, I guess it's nothing to do with overheating.
When it happens, the last thing that I see is the terminal and this message
*Jul 12 19:11:15 Username kernel: [ 257.855601] iwl3945 0000:03:00.0: Error setting Tx power (-5).*
before it logs out and takes me back to the login screen.
I was wondering if anyone has had similar issues and knows why this is happening. Perhaps I should file a bug report.