When it seems right is the best answer that I can give.
I don't think that many new players tend to bluff 'intentionally', rather I think that many new players just plain don't have any idea what they are doing and don't 'believe' that they are bluffing when they make those crazy bets that don't seem to make any sense. They think that their hand has a much better chance than it actually does.
It's a little different for spin and go
's. The type of person who generally chooses a spin and go is after a quick rush, be it a win OR a loss - doesn't seem to really matter. Regular players tend to choose spin and go's when they are frustrated/tilted and are looking to recapture some of their losses (been there/done that). Prime time to move in and pounce, btw.
Bluffing is a normal part of the game. Used sparingly and appropriately it can be a very powerful tactic.