Random shutdown after minutes for macbook pro 15" 2014
It's not clear to me what I reset completely macOS means? However, the first two things I'd do now are testing to see what happens in Safe Mode and to also reset the System Management Controller.

Boot into Safe Mode

Follow these steps boot your MBP into Safe Mode:


Fully shut down your Mac
Restart your Mac
Immediately press the Shift key and keep it down 
Let go of the Shift key when you see the login window (NOTE: If you have FileVault enabled you may need to log in twice).
Use the computer for a while and take note of what happens (i.e. is the issue still present, etc)
Exit Safe Mode by restarting your Mac as normal
Once you've booted normally again use the computer for a while and take note of what happens (i.e. is the issue still present, etc)


Reset the SMC

If the issue is still present I would reset the SMC. For your particular MBP, follow these steps:


Shut down your computer
Keep the MagSafe adapter (power cable) plugged in.
Press at the same time shiftoptioncontrol (on the left side of the keyboard) and the power button
Let go
Turn your computer back on with the power button.


Let me know how things went after doing each of the above.