At random points during the day (but not every day), when I've been working quite a bit, MacOs gives me continual freezes for 10-15 sec. This especially happens when I switch between apps and when I perform certain actions such as trying to reboot, switch a tab in chrome, etc.
The freeze is not a typical rainbow-ball-freeze, but literally, the screen is frozen. The music does keep playing (buffer?) but does not respond to commands, nothing does.
I run Mojave 10.14.6 and own a Macbook Pro 15" mid-2012 in which the primary drive is an SSD and I replaced the DVD-drive with a 7200 rpm Hitachi.
Most of my data, documents, videos, images, etc are on this second hard-drive. MacOS and apps all run on the primary SSD disk.
I'm not sure, but the freezes somehow feel faulty to the hard-drive.
I tried running First-aid on the data-disk but it's unable to unmount. I will try a reboot later, but in the past, the first-aid was unable to find any faults.
How can I proceed to find the root cause of these freezes?
I did the etrescan and although beachballing is not the right description, I thought it most closely resembled the behaviour. I removed something that might've been adware. I checked unsigned files, which are mainly developer tools I use.
I pretty much always run Activity monitor on the side to see if my CPU starts spinning up like crazy by some app. This is not the case when I have concurrent freezes. I also did a safe-boot and ran disk-utility health-aid and it did so without reporting any problems.
I just had the freezes again. It was very clear that the freeze happens whenever I do an action (switch app, open run, delete a file, type admin pw, etc). If I stayed in the same application, it almost all run perfectly smooth...