Ubuntu 16.04 on new PC crashes often

I have just bought a new PC with the following specs:
Memory (RAM) 64GB Corsair VENGEANCE DDR4 2666MHz (4 x 16GB)
Graphics Card 12GB NVIDIA TITAN Xp - HDMI, 3x DP GeForce - GTX VR Ready!
2nd Graphics Card 12GB NVIDIA TITAN Xp - HDMI, 3x DP GeForce - GTX VR Ready!
It has a clean installation of Ubuntu 16.04. Sometimes, even just by browsing the internet, or doing light coding (without the use of the GPUs), it crashes and I have to give it a hard reset. Other times, when I use code that requires the GPU, it does not crash. So the behaviour is highly random. Any suggestions?

Did you buy this from PC Specialist?

Does it happen under Windows?

Not saying you should be using Windows ofc, just that if it doesn't happen at all with a Windows install you can be fairly confident it's not the hardware.

What CPu are you using? I have run Ubuntu on three different PCS machines and Linux on four and never had a problem like that, my first guess is it would be hardware and not the OS, as Oussebon has suggested.

Also, are you using Ubuntu or Nvidia drivers, there have been driver issues with some GPUs in the past.