I recently installed Cubase PRO 8. everything was fine except for some random CPU spikes. they were specially noticeable while opening other programs or loading a webpage in chrome, for example
i read many posts, tried many things, changing drivers, configurations, disabling ASIO Guard, etc. finally what solved the issue for me is disabling the antivirus. eventually i uninstalled it. it was panda antivirus
i searched a lot for a solution and didn’t see nothing about this, so i hope this is useful for someone! 
Just wanted to say that I also experienced this same problem.
CPU would average 60-70% but would get burst of 100% every 30 seconds or so. Since I mixdown in real-time I actually couldn’t finish a mix as it kept aborting due to CPU spikes.
For me disabling Wi-Fi and closing a few background programs like spotify etc solved it.
Hi! In my case, i disabled my GPU and the problem seem solved, so far no pops or cracking sound after 2 recordings finger crossed
I am using this GTX 1050 GPU.
window 10
i7-8750H
16GB ram