The fact that the problem is intermittent and apparently random suggests that something in the OS is indeed swallowing all your I/O or CPU capacity for short period, and that something is unrelated to the DAW.
It could be the disk, but most likely is either some application that wakes up and does something, or even a Windows task (if you're running Windows 10) even if this is much less the problem it was in W10 early days.
Typical culprits are traybar programs that "call home" to check for update and start the download automatically, services installed by questionable software or in some cases viruses of some sort - which wake up and send data home. It can also be some corruption in your system, DCOM servers may behave bizarrely if they crash, with repeated retry and restarts which hog the system.
A disk check of course is never amiss, if you're using a rotating hard disk. That done, I'd start with checking the Event Manager to see if there's something amiss, look at the Taks execution schedule (also check that there aren't Windows updates in download and that you have scheduled "business hours" correctly - if you work in the evening the default probably won't work for you), check your services, use
https://docs.microsoft.com/en-us/sysint ... s/autoruns to check for suspicious autoruns.