Weird boot loop

[Sima01]

Hello,

 

I work in a small computer shop, today I received a PC that has "boot loop" but that boot loops goes through motherboard logo to windows logo display and then just suddenly restarts, i checked PSU, RAM, disks everything it just goes through that boot loop, tried removing disks, if I remove disks it boots to BIOS, MOBO is gigabyte B450 chipset, so to an naked eye everything checks out, could it be fault of te mobo to cause that loop, since even windows install will put it into the loop. Just want a second opinion before we send the build to the customer, ye i don't have any spare MOBO's sadly, i get really low budget to service it since its 3rd party system. Kind afraid of BIOS update since mobo just could go brick mode :P, and that would void the warranty even if i do it in the name of certified shop. It was working just fine for days as customer states and than started looping. Visual inspection didn't show neither leak or missing component.