Mac Mini "unexpectedly shutting down"

Question

Within the last week, my mini (less than two months old) has started suddenly posting a screen (black with grey/white writing), stating that it is has unexpectedly shut down after being on for about 20 minutes. I am instructed to hold down the power button and restart. The problem occurs when I am in different programs and when I looked at the report that was generated it was a kernel error. Any ideas of what the problem is or how to fix it? If the message comes up again (it hasn't the past two times), then I will copy it and post it here.
TIA-
Campbell

Answer 1

The problem with diagnosing this issue is that it's neither clear what was wrong with the system when it was repaired, nor what was done to resolve it at the time. While these events may have nothing to do with the present issue, they may be directly related.
As an example - you say that the system was not hot when it recently shut itself down, but had the repair involved removal of the logic board and the thermal pad wasn't replaced (as described as a requirement in the service notes) then it would render the system far more likely to apparently random shutdowns, because heat would build up more quickly and trigger protective mode with little apparent heating. That would also explain why the restart options don't seem to work.
Thus it might be a good idea to ask the repairers exactly what they did to the system when they had it, before contemplating a potential fault in the power unit.