hy, the report of the day :
After one night where my pc is off and the psu is on power. the system boots without problems.
I try again to test, on this night, with the mainboard to the power off. And i'll be back tomorow for let you know the result.
I think it was my sata cables, but like the problem seems pop randomly, i prefer wait again and give you my results, same if that's useless.
I hope don't face this problem again. For the others with similar problems, check my differents handling if that can help you.
Later, i test with "failsafe watchdog" activated, but i guess it was not my problem. When i have time, i'll put my older cables and test again