I'm doing nothing, I use it once a week or so, and it happens randomly... or not.
Always on Friday 9-Aug, 30-Aug and 20-Sep. and always between 14:50 to 15:10. I'll check this.
I've seen that when I restarted NodeRED, node.js change its version automatically.
From 16.6.1 to 16.8.1 to 16.9.1. Is it good?
You must have automatic upgrades enabled somehow. I don't use Windows so can't help with how that might be. Very likely it is associated with that.
When you say you use it once a week do you mean that node red is not running the rest of the time, or that node red is running all teh time but you only interact with it once a week?