If it's an i7 and a gigabyte board, updating the bios will probably be fairly problem free.
It may be a recognised problem with your motherboard and it may be worth googling "problem (your motherboard)" to see if anyone else has experienced the same or similar.
However, before going down the bios update route, I would try running the machine with the absolute minimum - one stick of ram, just the hard disk with the os and video card (on board video if it has it) no internet, sound etc. and see if the symptoms return.
It could be, a faulty ram stick, the motherboard may not like your particular ram (you say it has been doing this since build).
Is your power supply strong enough for what you are running - there are online calculators.
It could be a failing power supply - is it a good branded one one or a cheapo one?
Have you tried resetting the cmos - look in the manual?
When you built it, did you use heatsink paste between the fan and the processor?
By all means update the bios and, if you post your motherboard details, I will look and see if I can guide you through it (pm if you prefer) but I would look to other things first.