A shield takes 1 action to equip (PHB 146). I'm an new DM and would like to allow that in the first round of battle the PC may use the "interact with objects" time (PHB 190) to equip its shield, if not already equipped.
Reason I want to allow this is that I don't like the PC to always have its shield up, just in case there's going to be a battle.
Perhaps I'm overthinking this, but could there be any reason I might consider to not have this house rule?
EDIT: Based on the helpful feedback here, I've written this house rule as follows (and all house rules are discussed with the party before the campaign starts):
Provided that you are proficient with shields, you may equip your shield as an "interact with object" move (only) at the beginning of a battle. This house rule is not valid:
- When you have explicitly declared that you either have equipped or unequipped your shield.
- When you are surprised in your sleep.
- When you have your shield stowed and cannot reasonably have it ready at a moments notice.
At the DM's discretion (and with reasoning) this rule is unavailable or requires an acrobatics check. Example: A surprise attack in a location where you could not reasonably have expected this.
Rationale for this rule: Prevent micromanagement of player state.