After struggling for days with this issue I think I've fixed the problem for myself.
In the nvidia control panel, under "Manage 3D Settings" there is a Power Management option that was set to Adaptive. I set this to "Prefer maximum performance" and I haven't had the problem since.
Bearing in mind that I could duplicate the problem at will by loading up pretty much any game I'm hoping that this is the end of it for me.
Hopefully this will help someone else too.
Note I had mult-gpu mode disabled as well as Physx gpu acceleration as I was playing around with those settings too.
In the nvidia control panel, under "Manage 3D Settings" there is a Power Management option that was set to Adaptive. I set this to "Prefer maximum performance" and I haven't had the problem since.
Bearing in mind that I could duplicate the problem at will by loading up pretty much any game I'm hoping that this is the end of it for me.
Hopefully this will help someone else too.
Note I had mult-gpu mode disabled as well as Physx gpu acceleration as I was playing around with those settings too.