How about start up service on computer management>services and applications>services?
Set all of non essential service to manual, non priority service to delay start. You can find a list of thing you can change and not affect operation online.
What is non essential service? Sorry because I'm just a computer newbie.
I had that problem too. It was my hard drive
I recommend to try another hard drive and note the results.
I don't have any other hard drive but I'm PLANNING to buy a SSD soon, just PLANNING, 40% not buying in an emergency case.