I am guessing that you have an HDD. I have help four or five friends in the past couple of months who experienced the same, mostly at startup for about 5 minutes, then randomly during the day.
WHat I did was convert them to SSD. They were shocked at the improvement. No delay at startup, and performance was excellent.
The conversions ran from 256gb HDD to SSD, up to 1TB HDD to SSD. And, those SSDs are pretty cheap nowadays.
I used a my backup software to create the clone of the HDD to SDD, and all were successful.
Ok, you need to check if you have MBAM real-time, and WD real-time concurrently. They could be conflicting with each other. Also, I am a non-believer of MBAM's claim that they can run concurrently.
If they are running concurrently, choose 1 and kill the other.
Do you have any start ups that like to phone home? Are you allowing W10 to upload full diagnostic data, and automatic feedback? Do you have all those live tiles actually live?
There is so much data being collected, so who knows what is going on.
Let's start with stopping MBAM, and maybe even uninstalling it. That includes any cloud protection as well.
You do realize that Windows 10 has a whole slew of services that run in the background and it is possible that it is simply these services rearing their ugly heads?