I've just bought a new laptop last week (ASUS VivoBook Max x441u |6th gen. Core i3, 4gb ram, 1tb hdd, Nvidia GeForce 930mx running on Windows 10) It was working fine for a few days until I downloaded something and it turns out to be a virus. I believe it was the InitialSite 123 virus where it makes my laptop useless when opening a web browser. So I panicked and immediately reset the laptop. It took a while and it was finally done, it was still very slow. I noticed that the disk usage is mostly at 90-100% and makes startup and overall performance very slow. It takes about a minute and a half to boot up now and at start up the disk usage is 100% and lowers down after a few minutes. It seems to be only happening upon startup.It is still painfully slow and hoping to find a fix for it. Customer service told me to reset the laptop (keeping files) and was still very slow and it was never like this before. I've read forum after forum hoping to find a fix for this. So please, any help would be gladly appreciated.
You might want to also try running it in "Safe Mode" or "Safe Mode with Networking" and see how much faster it starts up. Now in that mode you can't run a lot of stuff, however since this is a starting up issue, it should help with sorting out what is the cause. If it runs a lot faster, then you would definitely need to go through what is launching at startup to weed out what is the cause.
You should also consider running some more good deep virus scans. A reset that leaves files on the computer (versus a full on reset) doesn't always remove what you need gone.