Gigabyte's Q-Code C5 seems to be related to Ram Memory.
Is your RAM listed under the Motherboard's QVL List by any chance?
Could be either a defective CPU or Motherboard or RAM Module.
I would run MEMTEST86 to eliminate defective RAM Memory.
I would install one Ram stick and see if the issue continue or not.
I would open a Gigabyte Support ticket (as long as your RAM is listed on the QVL List) and ask them if the Motherboard is defective. Reason why I mentioned if the RAM is listed on the QVL List is because most likely Gigabyte Support may not help you if you have unlisted RAM installed or say it is due to your RAM not being on the QVL List. but just hypothesizing.