A question came up in a new pathfinder 2e game I'm running, where a cleric rolled poorly at the start of combat and ended up at the bottom on the initiative order. When an enemy attacked, he claimed that since he was in a dungeon and knew it to be a dangerous area, he would have had his shield raised before combat started. Intuitively that sounds wrong, and I can think of a few narrative reasons it doesn't make sense, but if possible I like to have concrete evidence to back up my rulings.
Is this argument correct, or should he only get the benefit after his first round where he uses an action to raise his shield?
More generally, what would this mean for things like buffing cantrips (e.g. guidance) or having a weapon drawn?