Question System Keeps Restarting when it goes out of BIOS screen

Mar 26, 2020

I have an issue with this Combo: Gigabyte GA-H110-D3A+intel Celeron G3900, I won't continue with the rest of the spec because I have changed am for several times without any changes.
When I'm trying to start the system it loads the BIOS screen (i mean the screen where u can click the key and enter in Bios) and if I won't go in bios after a few sec it shuts down and restarts again and again. but if i go into BIOS it works fine while I'm staying in it, i have upgraded to the latest BIOS just to get a chance but still the same.
what i have tried so far:
  1. lot of amount RAM in both ports, single/dual, the RAM s that work 100% fine on another system.
  2. at lest 3 different PSU
3.several HDD/SSD/USB
4.several GPU-s as well as minimum 4 different types of GPUs.
but the problem persists so far. i really don't want to waste more money for CPU to check the only thing that i have not changed.
i contacted to Gigabyte directly but they said to contact to seller witch i can't because there is no more guarantee on it.
it bought it a new tested and in a few tries i gave up tho that it was problem with PSU until i have not changed all the parts as i mentioned above, but strange thing is that once it worked for a day normally and when i tried to load another day system was faulty again.

Thank you for