Do you close the psu over night or for a longer time?
I do with mine and when i flip to on my pc starts fans and every thing for 1-2 sec and after 10 sec is opening in bios idk why i use an evga 1000w gq
If the PSU starts, it can be something related to its startup, and the possibilities are: faulty PSU, faulty MOBO, discharged CMOS battery, faulty Power On button. You will need to search by elimination.