Computer shuts down after some minutes

[Googolplex]

EDIT: The reason it shuts down now is because now the weather is warmer (unless you live in the north pole or something) and the cpu is getting even hotter. During the winter, even under gaming, maybe you were getting away with 85°C which is not normal but still...operational.

I live in germany, we have almost summer, but just 16°C or sth. it's not the weather;-)

EDIT 2: Alright fine, don't buy any cooler or something. You could remove the cooler all the way, clean the cpu and heatsink from old thermal paste, apply new one, connect the fan and try again. That's my recommendation. Otherwise, I suggest you take it to a "professional" who will do the same steps.

That's what I already did before, but games still kill my PC.
But I didn't bring it to a prefessional.

you don't need to overclock for the cpu to move from voltage to another. For instance, I had no problems when on 1.1 but when it moved to 1.4 it instantly increased temp.

My bios doesn't allow voltage options. Just stock voltage and "ignore".