Hi,
You have 2 screenshots with the "Idle process" at about 90%, so in those screenshots the VM was actually not busy.
The other one however with the "NT Kernel & System" at 91% is interesting. If you happen to see that a lot then that can mean a number of things.
It could mean that your VM has too many virtual CPUs assigned (this is common, you mentioned you lowered/increased something, not sure if that also includes lowering the virtual CPU count) or it could mean that the host itself was too busy.
Or of course it can also be due to something else, such as an antivirus product being too "helpful".
If you have an antivirus product installed, then I recommend uninstalling it for testing if it is causing this problem. Sometimes you can get away with disabling the antivirus product, but most of the times an uninstall is required to exclude it from the possible causes.
For an antivirus product at the host you also want to exclude scanning the virtual machine (either by excluding the folder where the VM lives or by excluding the file types, most notably the .vmdk files)
Another possibility is that the VM is trying to defragment, or that some of the physical hardware is misbehaving (most often disk).
It is also recommended to disable shadow copies in the guest OS.
Oh.. more ideas.
Are you sharing a folder from host to guest via shared folders? Try to disable it.
--
Wil