PC lags/stutter while downloading at high speed

Jul 15, 2018
When downloading at high speed, my pc started getting lags, even mouse started lagging, making almost hard time to at least stop downloading, youtube sound stuttering. Yesterday pc just completely freezes while updating Blizzard Battle Net game. It happens at every huge file and when downloading cross 700kb border to 1.7-2.5mb for longer time. Only option is to restart PC and everything works ok until some time, i dont know when this starts, maybe after waking up pc, after some cache/memory filled. HDD runs at 100%. Yesterday i even got a popup about reconnected audio while lagging. This issue bugs me about a year, that means i run through several win updates with no fixes.

I tried:
1. bcdedit /set useplatformclock false
2. uninstalled antivirus
3. Checked for updates at Intel drivers
4. checked my sshd ST1000DX001 - which should have 7500rpm
5. Set Virtual memory - 7.6gb to 50gb
6. runned Malwarebytes and CCleaner
7. proxy check - disabled
8. closed almost every background programs

PC stats
i7, 32gb mem, LAN I219-V, GC 1070 Ti, its relatively new pc, so i suppose there is no need to flash bios. Dunno if i'm working on IDE or IHCI

Thank you for answers