FPS Drops in game randomly

Hi, I have a laptop (4 weeks old) with this hardware:

Alienware 15 R3. I7 7700HK processor Nvidia gtx 1060 16gb ram 256gb m2 nvme ssd

This computer should be good enough to run league as my old i5 with no discreet graphics card ran it fine. However in game I often drop from 120 FPS to 76FPS (however it stutters and looks like 20 FPS) just randomly, then it will stay there until I tab out and back in. It also happens when running Chrome in the background. Is this a League issue?

It does not happen when many things are going on, it just happens out of the blue. I have all the latest drivers, I have reinstalled League twice, reformatted my HDD and reinstalled Windows. My computer temp is fine, and it even happens when I've just turned the laptop on. I have my frames capped at 120 in game, my settings are medium. It can run 120fps often, even with many things happening in game. It's like it just decides to stop that randonly.

I am at a loss for what is causing this?