Zwift crash. Reboot required

Hi everyone, it’s the second time in a row that zwift freezes while I’m going and nothing works anymore (no CTRL + Alt + del). The only way out is to turn off the pc. Everything has always worked out perfectly. The first time he did it to me after about 10 minutes of play, yesterday 3 times in a row as soon as he entered to pedal. Then after the third reboot everything was fine for more than an hour of training.
Will it be the game or the PC? Could it be the cold? I have the pc fixed in the cellar at about 10/12 ° C.
Thanks a lot.

If someone can help he needs more information: