Perfomance issues -- probably related to fan control

[LordOfFrost]

Hello! Recently i've started to encounter strange issues with perfomance. After i launch almost any app that requiers any CPU usage above nonexistent, i experience heavy lags, stutters and all that kind of stuff. It involves games, media apps, sometimes even in-browser media. As far as i learned, it happens both on Nvidia and AMD integrated cards. So after some research i can share some factors that are (in my opinion) relative to the issue: 

1) Despite notebook case being pretty hot (above average at least) it does not switch the fans to somewhat high speed, they are pretty much sitting at bare minumim the whole time (except for the times, when CPU temp goes up to whopping 80 degrees)

2) Frequency drops to minimum.  And by minimum i mean 318 Mhz. It shows in windows task manager, Open Hardware Monitor and pretty much any other app, so i think that it is somewhat trustworthy information. 

3) Usually, when you start the PC, fans on it go to a full speed (probably to self-check) 2 or 3 times. It didn't happen for the last few days. No errors at startup though. 

4) All of this has happened both on the old (installed for about a year) and a fresh (installed an hour ago) windows 10 systems. 

5) There were no hevay stresses before it started to happen. Just closed notebook at work, opened at home, ran into issues. 

6) It sometimes solves itself. 3-5-10-15 reboots in a row (or shutdowns - turn on's) solve the issue... Until the next shutdown/sleep/hibernation. 

7) Outside of mentioned problems, everything else works fine. 

😎 I use compressed air to carefully clear dust off the fans, so that's not an issue. 

So, i kinda ran out of ideas. Internal tests (which are in the BIOS) pass and tell me everything is okay. There are no in-windows errors. There are no critical errors in the system logs. It just kinda doesn't work, that's all. 

Should i search for a service centre already, or is there some other option i may try to diagnose the trouble? 

[LordOfFrost]

So right after i've posted this thread, i decided to reboot again and it got even worse -- now the CPU straight up stays at 0,39 Ghz, no matter what i'm doing on the notebook. I mean, windows load-up, opening browser with this exact page loading (slowly and painfully) didn't bring it any higher. Here is a screenshot too.