Windows 10 Perfmon - Maximum Frequency jumps

i have a problem with my new laptop. Whenever i try to play a game, after about 15-20 minutes of gameplay, i started to get periodic stutters that can't be tied to the game itself or what's currently happening on screen. After trying out a lot of things, including changing everything in the game configs and even going as far as calling my ISP for support (because i thought it was a problem with the inteet, even though my ping was constant) i went and started to watch my pc closely with perfmon /res when playing the game. After just a few hours, i realized what my problem was:

Maximum Frequency starts going up and down, dragging CPU usage with it.

Now, it should be noted that my usual Maximum Frequency is at 120%. But after playing the game for the previously mentioned 15 minutes, the frequency starts jumping up and down wildly, dragging the actual CPU usage down with it, causing those 2-3 seconds stutters.

I tried the following things: 1. Locate PowerStep or similar in my BIOS/UEFI - No success, i can't see anything in there that would relate to that. 2. Disabled power saving while not on battery - I actually almost never use the laptop while not on battery. 3. Set minimal processor state to 100% while plugged in.

So, i'm a bit at a loss here, i have no idea what could cause this kind of problem. Could you help me?

Specs:
Processor   Intel(R) Core(TM) i7-5500U CPU @ 2.40GHz
Manufacturer    Intel
Speed   2.4 GHz
Number of Cores 2
Video Card 1    NVIDIA GeForce 840M
Manufacturer    NVIDIA
Chipset GeForce 840M
Dedicated Memory    2048 MB
Total Memory    4.0 GB
Video Card 2    Intel(R) HD Graphics 5500
Manufacturer    Intel
Chipset Intel(R) HD Graphics 5500
Dedicated Memory    128.0 MB
Total Memory    4.0 GB
Memory  16 GB
Operating System    Microsoft Windows 10 (build 10586), 64-bit