Hello Kevin, thanks for your help.
Now, only Legacy mode is enabled in BIOS boot options.
I'm testing reboot with Windows 7 64 bit in same hardware type: the system reboot well after 3 days of continuous reboots ( every 5 minutes);
I'm investigating Linux advanced boot options :
to get some answer, but not knowing the specific problem cause, is not simple to find a solution.
if you have any indication About the likely area of interest, I can do some tests using these options.
I'm agnostic about OS "religions" ;-)