Graphics card cuts out / crashes when playing high-performance games?

I have had the same problem for a long time (since the current graphics card). My graphics card assumes that more graphics-intensive games (such as Overwatch, Hitman etc.) are started. That means both screens (UHD) go black and go out. The LEDs in the PC and the fans stay on. Sometimes the typical mainboard beeps sound (1x long, 2x short, i.e. Graphics card problem) and then the PC goes off. The next time you start everything is normal. This is not the case with games that are not that complex (e.g. League of Legends or Minecraft).

Note 1: All drivers were and are up-to-date, as is Windows.

Note 2: Everything was fine with the previous graphics card (GTX 770).

So what could be the reason? Thanks in advance!

My system:

OS: Windows 10 (Home)

CPU: i5 2500k (overclocked)

Graphics card: NVIDIA GeForce GTX 970

Mainboard: MSI P67A-GD55

Power supply: Antec 520

(SSD, HDD, 16GB RAM)

This means that your driver crashes at the moment and refuses to work and then has to start again; the only way I know to fix it, test you through the individual driver versions, or reinstall everything via ddu uninstall…

(ps if you have no on-board graphics or if it is switched off, you no longer have a picture in normal mode, only in bios and safe mode.)

Power adapter?