Normally this indicates that your GPU is overloaded, and OBS can't complete its compositing tasks as a result.
Are you gaming on this system, and capturing the video through your capture card for some reason? If so, why? You shouldn't do that. It causes significantly MORE system overhead than just using a Game or Window Capture... like driving across town and back to visit your neighbor.
You can also try running OBS as Administrator if that's the case, which should allow OBS to reserve some GPU time before the game can eat it all.
In any case, it would also be a good idea to download GPU-Z and make sure your GPU is running in x16 mode and hasn't been split to x8. If it has, you may need to force it to x16 in the BIOS, which also may mean having to move your capture card to another slot if it's in one that shares/splits lanes with the slot your GPU is plugged into.