Are you shutting down all non-essential programs (especially anti-virus) before starting the game? TeamViewer, for example, has been known to cause a similar problem, at startup (with various games), when running in the background.
When the game is minimized, can you right click on the Task Bar button and select Maximize or Restore?
Try starting the Task Manager (Ctrl-Shift-Esc or right click an open area of the Task Bar), switch to the Applications tab, then try right clicking and select the Switch To / Bring To Front / Minimize / Maximize options.
Try disabling the Steam Overlay for the game (right click the game in the Steam library and select Properties, then switch to the General tab).
In the graphics options, try switching to Fake Fullscreen display mode, to see if that will make a difference (can help with issues Alt-Tabbing out of games, as well as problems a couple people have had running D:OS 2 in Steam Link or BPM after recent Windows updates).
