Client forced my focus out of game [CLIENT]

It was a strange one-time bug, where after I got in-game, 5 minutes in, the game minimized itself to force my Windows to focus on the client. It happened again 15 minutes later.

I had to actually close the client itself and then reopen it (log back in) to prevent it from happening again.

After that game, I restarted the client and went in game, and the bug did not return. I was wondering if what I was experienced was unique or if others have had issues like that.