Does anyone have any suggestions for sudden delays with all programs even typing?

My relative has a Inspiron 13-7873, less then 2 years old and in the past few months everything got slow, even typing has a delay, audio sounds stutter and most transactions require you to walk away and come back. I have run diagnostics and other hardware tests and everything comes back fine.... I tried a factory default restore, this even had no effect. I now used my own media to wipeout and reload Win10 still pretty much slow. I can try replacing the m.2 drive even though it does not fail any tests I can replace the memory even though it tests fine but short of this, I am unsure what else to try, does anybody have any suggests? I would like to fix it and give back to my relative if possible...

Thanks

S