when the computer has gone into sleep mode or been switched
To me this sounds like a PC or video card issue. That's also a very power hungry GPU so you need to talk to the PC maker about the PSU and more. I've seen folk have to fit 750 to 1000 Watt PSUs to drive those.
I feel for folk in this position since they often find there is little support for gaming PCs they made themselves or integrated on their own.