Hi,
I have a similar problem.
After updating the BIOS of my motherboard (see my signature) to version F22a, I am not able anymore to start my formerly working OS X 10.11.6 system.
It automatically restarts at the very beginning, after writing the sequence of "+++++++++"
Is anyone experiencing the same problem? Could you provide me working BIOS settings for Gigabyte Z170X Gaming 5?
Note: I've noticed that after updating my BIOS, its settings were reset to default, so I've tried to restore (by heart) the previous ones.
Thank you.