You should go in to your nVidia settings and set dolphin to use the better GPU and not to use power saving features. (In theory this isn't necessary, as it should change automatically when started, but this may help.) If you changed any other settings, try putting them back to what worked earlier.
OS: Windows 10 64 bit Professional
CPU: AMD Ryzen 5900X
RAM: 16GB
GPU: Radeon Vega 56
CPU: AMD Ryzen 5900X
RAM: 16GB
GPU: Radeon Vega 56
