That just happened to me today and I don't understand why. How can I fix this? I'm getting 50 FPS or something.
50fps are not low.
Do you have the energy mode "energy saving mode"?
Or you did something ingame that your PC didn't like.
Do you have shaders or texture packs installed?
No energy saving mode, not done and no shaders or texture packs.
Does your game stay constant at 50fps? Have you limited the FPS in the settings?
No, sometimes above 00 FPS but mostly below 50 FPS. Yesterday it was over 200 FPS.
Did you play multiplayer? Or maybe with someone? It could be because of that.
I played multiplayer.
Well, then it should be clear. In multiplayer (no matter which game) you will lag very often. Most of the time it is due to other players' internet connections or even yours.