Question Monitor turns black while gaming ( Audio still on )


Jan 26, 2018
Hello and good morning everybody.
Im facing a problem with my pc. While gaming my monitor turns black ( also says no signal), audio is still on.
I faced that problem while playing PUBG (after 2-3 hours of playing) and with Fortnite (like 30 mins after i launched it).
League of legends is running with no problems ( i played 4-5 games in row ,no black screen).
My specs are :
Ryzen 5 2600 ( Stock cooler)
2x8 DDR4 RAM
Asrock Fatal1ty B450 Gaming K4 Motherboard
GTX 970 Palit Jetstream GPU
2 Case fans
2 SSDs (60GB and 120GB)
1 HDD (500gb)
520w seasonic m12ii evo PSU
Samsung SyncMaster P2250 Monitor

I downloaded MSI afterburner but havent checked the GPU's temps while gaming yet, i will do later today!
Any thoughts ?
**Important note : I just got my 970 two days ago from a really trusted person. I had no problems with my previous 960 tho.