The Xbox Series X crashing Cold War has a couple of common possible causes. Activision recognizes two major factors leading to crashes on Call of Duty: Black Ops Cold War: accidentally launching the wrong version of the game, and playing in 4K. Here's how to avoid crashes related to these two causes.
Xbox Series X Crashing Cold War: What Causes Crashes
The more insidious cause for Black Ops Cold War crashes has to do with the Xbox Series X/S launching the wrong version of the game. If you purchased the Cross-Gen or Ultimate Edition of Cold War, you'll have two versions of the game in your library — one for each console generation. Launching and playing the version optimized for Xbox One when playing on Xbox Series X/S can cause the game to crash.
To avoid this, use the filer to select "Optimized for Xbox Series X|S" in your game library. This will limit the list to include only the properly optimized version of Cold War. You'll be able to tell you're launching the right version because it will show the Xbox Series X/S logo on the game's tile.
The other, more obvious Cold War crash causer is running the game in 4K. Activision is currently investigating crashes caused by playing in 4K. To avoid this, simply run the game in 1080p until a fix is announced.