MacMini 2010 boot fails a minute or 2 after spinning wheel starts up

After being stored for a few years, My MacMini 2010 initially booted up and ran with the internal hard disk running a couple of weeks ago. Before it had been stored it was running with an external running 10.13.6, but that time it failed to an older version that I failed to note down. Now the internal drive is failing when I try to start it up. After I push the button to power up, will display the Apple logo after a little while, then after another little while the spinning wheel starts to spin, than after a few minutes it just turns itself off and does nothing. I have installed backup external drives with CCC copies of the external, but they don't book up, although they test as good drives in Disk Utility. Any idea what's going wrong and what might work to get it running again? Is it more likely to be a problem with the hard drive, the Mini or something else? I have other backups of the data, but like having an extra level of backups.

Thanks,