It all depends on how much memory is being consumed, how many programs are running, viruses, etc.
Starting with memory consummation- if you use too much memory on your computer it will slow down. Imagine a large box filled with various papers. The box is your computer’s memory and the papers are the programs inside. Try searching for a file labeled ‘Stone Sour’. There are tons of other papers and files in there and it would take a while. Try cleaning out your computer’s software every once and a while.
Running Programs- When I first got my used laptop, I found out that there were 64 start up programs slowing down my computer’s operation. Try and disable all of the unnecessary start up programs so it’s not doing advanced calculus when it first wakes up.
Also try not to run many programs at once. When you get done with one thing, close it.
Misaligned Files- This is when parts of a file aren’t where they were programmed in and the computer has to look for them. Like looking for a lost item.
Viruses- Don’t even get me started! You can Wiki this crap.
All in all, get your computer checked out and set up some reliable anti-virus software. By reliable I mean Google it and see what other people thought about it. You may even want to run a thorough virus scan to make sure nothing is amiss. You could set up a few complicated firewalls on your own, too.
Also, listen to the other people on here. They may know more about hardware than I do (like @jerv and his comment about it being mounted properly) , because I know little to nothing about that. I do know the aforementioned things about software and tons on viruses (that’s why you need to Wiki it because I could drone on and on about viruses and malware).
I hope this was helpful because I’m not sure how much you already know so I just typed the things I thought might be useful.