Question my moitor keep changeing its hz

[talptz]

my monitor keep changeing its 240hz to 144hz
after i dont use it for a while in the nvidia

i notice 2 metod to fix it
1) rebot the pc
2)unplug the display port from the Graphics Card

i dont know what causes it to occur
any suggestions?
til now i was thinking it related to my elgato card
and that i clone my main monitor but the seceond metod of unplung it from the Graphics Card and replug it
tell me the elgato is not the reason

 

[Ralston18]

Update your post to include full system hardware specs and OS information.

Make and model monitor? Connectivity (DVI, HDMI, DP)?

Single monitor setup?