Why does my computer keeps jumping out of game windows?

[Stretchytall]

This week, my computer started randomly jumping out of games I'm playing in fullscreen to other windows. This is bad because it pulls me out of competitive games when I'm in the midst of a fight.

When my computer jumps out of the game window, my mouse cursor usually has the processing circle next to it, suggesting the computer is working on some process. But I don't know what it's working on or why it's causing the computer to jump out of my game window.

Any advice on how to troubleshoot this problem? I don't know why it's happening. It never did before several days ago.

Help appreciated.