Cubase shutting down iMac

I have been using Cubase 7 on an iMac (Sierra 10.12.6) with no issues for more than 3 years. The last mac updates were about 3 weeks ago and no issues. Then today all of a sudden when I start up Cubase, about 1 minute into the startup the whole computer shuts down… Have tried several times now.
Can anyone assist on how to resolve this issue?

There nothing in Cubase that can shut down your system. The problem must be elsewhere.

To troubleshoot this, I would unplug all hardware from the Mac and restart with a P-ram reset.