I have had the same issue for a few weeks (possibly related to 0.8.33). I am playing on an Xbox one, and the game either freezes on the signing in screen or during a ranked match.
When it freezes, it quits Gwent and throws you to the Xbox homepage.
Over the past few weeks, it has happened 20+ times (minimum 3 times per day). Yesterday evening, it crashed 3/4 times in a row on the loading screen. There is no error message. I tried both deleting my saved game data and reinstalling the game, but neither did anything to improve.
Only when I took out my ethernet cable and played using wifi did it seem to be much more stable: it did not crash for the rest of the evening (2/3 hours).