Originally Posted by
AOD_Tymplar
What does the inside of the box look like? :)
Could be heat. Keep it clean of dust and such internally? Sometimes dust will "cake up" around fans and heatsinks and cause things to run sluggish and then eventually crash.
Specs sound pretty decent and can't imagine the performance being from that, unless there's just something like a thermal issue or a rooted malware / virus that's not getting picked up or the like.
You ever run Malwarebytes just to be sure? Check out CCleaner as well (free also). I would defrag the HDD and "optimize" (trim) the SSD just for good measure. And also, maybe just scan both for errors (same screen where you'd select optimize).
Perhaps something to give a go and see if you get some positive results?