It seems that sometimes the computer will automatically run through though an annotate a game but I don't know how to toggle this feature on and off. thanks.
It doesn't toggle. You can request it for a game by going to the "Analysis Board". Under the board, when the computer analysis tab is selected, there is a large button for requesting a computer analysis. You are not restricted to only your own games, you can request an analysis of anyone's game. But you are restricted to analyzing no more than 30 games a day.
I think the automatic analysis might be part of lichess' anticheat. I notice it happens every time I play a rated game in a new time control.
The "automatic" analysis could also just mean your opponent (or possibly someone else) requested an analysis before you did.
