Mac Pro (High Sierra) randomly shutdowns & screen flickers

Consider downloading and running this little "discovery" utility, Etrecheck. It changes NOTHING. Etrecheck was developed by senior contributor here, and uses system calls to collect often-needed information.

it contains little tests for speeds of devices, CPU utilization, memory usage, energy usage and a digest of recent problems, in one easy to use package. it does not even need to be Installed. Because less can be learned when your Mac is running great, best time to run is when your problems are actually occurring, if possible.

if you follow the directions faithfully, its report (pre-laundered of all personally-identifiable information) can be "Shared" to the System ClipBoard, then Pasted into an ‘Additional Text’ window in a reply on the forums.

Use Etrecheck Pro for free:

http://Etrecheck.com

the start a reply on the forums, click the additional text icon, and PASTE

...

Kernel Panic Reports are stored in the Folder at:

/Library/Logs/DiagnosticReports

If you copy and paste that string into:

Finder > Go menu > Go to Folder

it will take you to the Folder where those reports are stored.

Kernel panic reports are named with Date&Time and start or end in ‘panic’

If you find one, please post as much as you can here, by using the “additional text” Icon in the reply footer (looks like a paper with writing). (Once the report devolves into incessant software-names or incessant Base-64 dumps with lots of AAAAAA lines, you are done.)

Please don’t post more about 20 lines of any other types of reports — they are interminable, and any information useful for this purpose is on the first screenful.