Apple recommends an unusual procedure to fix this, which might also work with other models suffering sudden shutdowns.
shutdown
What are the benefits to leaving your Mac running all the time? And the costs? Which should you choose to do?
Stepping through key points in the log as Mojave 10.14 starts up. Most of the key waypoints are similar to those in High Sierra.
Is shutdown -r now better than reboot? What advantages does Finder’s Restart have over them? The answers are in these logs.
When your Mac seems unresponsive and its GUI frozen, you don’t have to reach for the Power button. Try connecting using ssh: it’s actually very simple and valuable.
Shutdown cause codes, wake reasons, ACPI, and sleep states – diagnosing problems from hardware events.
Some subtle improvements which make it much easier to use when working with saved logarchives. A final release candidate?
This makes it much easier to perform repeated analysis and search on logs captured to cover important events, such as crashes and problems.
How to interpret the code numbers written into your Mac’s log to indicate the reason for shutting down, restarting, or going to sleep.
Sometimes you can’t use the menu command, or it doesn’t work. What do you try next?
The Eclectic Light Company 