MBP Mid 2014 randomly shutting down

ThomasL-HH wrote:

Thank you! Tried all of them, to no avail. The MBP even shut down when in safe mode.

I've not having any unusual shutdowns after installing gfxCardStatus and "disabling" the nVidia graphics chip.

Good computing ThomasL-HH ! Thanks for your report—sounds like it solved your problem.

ThomasL-HH wrote:

For about 6 weeks (right after upgrading from Mojave to Catalina 10.15.5) my Mid 2014 MBP is shutting down more or less random. Note all of these shutdowns are not unexpected, i.e. there is no "Unexpected" dialog shown after power up.

It started as shutdown when going to sleep, right after the screen saver disappeared. I restored Mojave from TM, but the problem persisted.

After a clean Catalina install, the problem was still there, but less frequent.

I suspected a thermal problem, so got my MBP a cleaning job and new thermal paste.

After upgrading to BigSur, these shutdowns occur more frequently again, even while working. Intel Power Gadget shows no unusual load or temperatures.

I resetted PRAM and SMC more often than I can count.

Any hint to where I should look?

Uninstall all third party apps that are Cleaners/Optimizers/Anti-Virus typically this cause issues like you describe.

To trouble shoot further you can:

—Try a SafeBoot https://support.apple.com/en-us/HT201262

Takes noticeable longer to get to the login screen, does a 5-15 minute disk repair before it fully boots up, and certain system caches get cleared and rebuilt, including dynamic loader cache, etc. Login and test. Reboot and test as caches get rebuilt.

In Safe mode third party system modifications and system accelerations are disabled, it removes malware, etc hampering smooth operation, however a reboot will put it back to normal mode.

This test will tell you if third party interference; extensions etc are not loaded in safe boot mode.

—Test issue in another user (or guest user) account  https://support.apple.com/en-us/HT204443

This will tell you if it a universal issue or isolated to your user/admin account.