Laptop shuts down unintentionally?

I have already done everything in the system settings regarding energy saving mode etc. And have actually set my laptop so that it should NEVER go out, neither standby nor completely off. Well, he does it anyway, especially when playing and of course always in a team fight, that's really extremely annoying, he often does it every 30 minutes, sometimes a little less often, but also like when I e.g. Watch Netflix.

It does not matter whether the charging cable is connected or not, it then simply shuts down, sometimes there's a very short message with ' Power saving '' before it switches off, although the laptop is fully charged or attached to the cable.

So something can't be right here
I only bought the laptop, it is used but has been completely upgraded and has a guarantee on it.
I'm very happy about help!

Difficult to say, I would look at the system event viewer, remember the time at shutdown, restart and then do a screen of it next.