Apparently Win key + d toggles the desktop. Assuming something is not resting on your keyboard, any chance you're accidentally hitting this key combination, thinking you're doing something else?

Discord keeps popping up when I add/remove monitors (turn on/off my TV), but nothing unintentionally showing the desktop as you are getting.

Thank you for your reverting back. This is not like that, that games automatically minimize the taskbar without pressing Win+d.

By the way, I have resolved the issue from here. And now I play games without disturbing and the taskbar doesn't minimize.

Thanks.

There are 6 solutions listed there. Could you tell us which one worked for you?

This is the 2nd solution that I solved from the article. Actually, my GPU driver was outdated and I just updated the GPU driver from the device manager and the problem got solved.