Question HDD sometimes load stuff fast,sometimes slow

[Popikaify]

Its some random 7200rpm hdd,sometimes when i enter a game (world of warcraft) it loads assets,characters and so on pretty fast,but a few minutes later it can become really slow...whats going on ? is there a way to fix this,delete some cache folder or anything that could be corrupted.

 

[rgd1101]

defrag the drive?
malware scan the system?