Hi there Altwolf,
Try running your system in safe mode. In case the problem is gone, there is a possibility that all of this is software related. In case it is not, it is most probably hardware.
In we assume that your RAM(most probable cause) is fine, you can do the following:
- Measure your system's temps.
- It could be PSU. Unfortunately, the easiest way to see whether this is the case is to just borrow one from somebody and try it on your system.
- Update your GPU drivers.
Cheers,
D_Know_WD