Apologies. I was away the rest of the day yesterday. That would be my best guess as well. Seems like the web browser you use for Construct 3, may be automatically clearing cookies/cache. Or perhaps like — mentioned, it may be automatically connecting to an incognito tab.
If neither of those are the case. Do you have any applications on your machine, that automatically clear web browsers cookies/cache? I use CCleaner to clean my PC every once in a while, but I disable the cookies/cache/filled forms clearing in Chrome, and Brave for this reason. It just makes it easier for me, not having to enter everything again. I also use the Desktop App/Shortcut for Construct 3, which opens up in Brave(my default browser). If I clear those three things I mentioned above, I need to enter my username/password for everything Construct/Google Drive related, as well as the Settings info in Construct 3 like Default creator name, website, and any other settings there.