My computer is now intermittently failing to boot up.

For the last couple of days, when I turn it on it hangs on "AHCI Drive Init...", and when powered off and on again, it booted up fine.

Today, it did the same but failed in a few other ways too, seemingly at random:

• Hangs on "AHCI Drive Init..."
• Boot loop (after "AHCI Drive Init..." appears for a split second (no drives listed))
• Black screen (after "AHCI Drive Init..." appears for a split second, a black screen with all fans still running)

The interesting part is that the above is not affected by what drives are connected, or what to. I have tried both disks, each disk individually and no disks (along with trying the primary and secondary SATA controllers), none of this has any effect on what happens.

After about 20+ attempts of different combinations, it suddenly decided it would boot up into Windows, and I hadn't touched anything for about 2 cycles.

Motherboard: Gigabyte GA-870A-USB3
Processor: Amd Phoenom II x6 1090T
RAM: 8GB Corsair 1600
Primary Disk: Plextor 128GB SSD
Secondary Disk: Western Digital Black 1TB
OS: Windows 8.1

Is this my motherboard dying? Or could something else be the cause?

Thanks!