Quite recently, a strange problem has started.

Rather frequently, every once in a while, I lose focus of the window/program/app that I am currently focused on. Sometimes, the computer regains focus automatically after a few seconds. Sometimes, I haven't to manually click back on the program to regain focus.

E.g. I'm talking away in Notepad, when suddenly, computer loses focus, causing whatever I type to be fruitless. Thus, I have to regain focus to begin typing again.

Has anyone experienced this before? Any tips?

I've tried Google, but the solutions that have come up are rather tedious.

I suspect some service or other program or process is causing this, but I have no idea what.

My best guess would be some program that is making temporary windows (possibly invisible) but not putting them in the background or some program is randomly putting its window to the foreground while still being hidden.

Pinpointing this can indeed be tedious.
My bet is on malware running in the background. Try running a online virus check and try a few malware scanners.

If nothing comes up I'd try restoring the system to an earlier state.

Also this seems like a good idea.

Turns out it was an Apple Mobile Device service that kept trying to turn itself on, even though it would repeatedly cause an error.

Fixed.

As I said, malware...