Thanks for reaching out. I am sorry to hear that your Google Nest Hub is randomly rebooting. I definitely understand your concern.
Could you please try to do a Factory Data Reset on the device? The device will erase all data and settings.
On the back of Nest Hub, press and hold both volume buttons together for about 10 seconds. Your Nest Hub will let you know that it's resetting.
Note: You can't use your voice or the Google Home app to factory reset Nest Hub.
Please let me know if this helps resolve the issue or not. I look forward to your update.