Can a creature choose to squeeze into a space when not forced to do so?

Question

In Pathfinder (not 2, and other systems for comparison would be interesting for comparison but are not the question)...

Assuming you are large or larger, and expect a square you occupy to later be attacked, can you squeeze of your own choice?

For example, a huge or larger creature backed up against a cliff who expects to be targeted by arrows, can they 'press themselves to the wall' squeezing into the space nearest the wall, otherwise following all squeeze rules?

Or similarly knowing that a square is trapped in a hallway can you squeeze to walk past without setting it off?

Answer 1

As long as the space is at least 1/2 the character's normal size you can squeeze into it with the following penalties:

• movement while squeezed cost twice as much
• you take a -4 penalty on attack
• you take a -4 penalty to ac

So, I doubt it would actually, by the rules, be helpful to the giant avoiding arrows, although, if you find a good reason, any creature can voluntarily squeeze.

See: https://www.d20pfsrd.com/gamemastering/combat/

Squeezing

In some cases, you may have to squeeze into or through an area that isn’t as wide as the space you take up. You can squeeze through or into a space that is at least half as wide as your normal space. Each move into or through a narrow space counts as if it were 2 squares, and while squeezed in a narrow space, you take a –4 penalty on attack rolls and a –4 penalty to AC.

When a Large creature (which normally takes up 4 squares) squeezes into a space that’s 1 square wide, the creature’s miniature figure occupies 2 squares, centered on the line between the 2 squares. For a bigger creature, center the creature likewise in the area it squeezes into.

A creature can squeeze past a creature while moving but it can’t end its movement in an occupied square.

To squeeze through or into a space less than half your space’s width, you must use the Escape Artist skill. You can’t attack while using Escape Artist to squeeze through or into a narrow space, you take a –4 penalty to AC, and you lose any Dexterity bonus to AC.

Answer 2

RAW, the answer is no

The Squeezing rule states:

In some cases, you may have to squeeze into or through an area that isn’t as wide as the space you take up. You can squeeze through or into a space that is at least half as wide as your normal space. Each move into or through a narrow space counts as if it were 2 squares, and while squeezed in a narrow space, you take a –4 penalty on attack rolls and a –4 penalty to AC.

As you can see from the rules, the act of "squeezing" is always related to an area not wide enough to contain the creature/character. If the creature/character is inside an unoccupied square and free arean the game assume you occupy always all the squares you are in.

Finally, if the square is trapped, even if you squeeze, the trap is set off. In a square with a trap, by rules, the square does not have a safe zone to pass through (of course, this is a general state... the GM can allow to squeezing to pass a trap).

What can you do in your situation?

Using the rule, simply, your creature can use stealth to hide itself and prepare an ambush (a counter ambush in this case?).

Create a houserule and allow to squeeze even in standard squares.

Keep in mind anyway... that what are you saying here:

[...] For example, a huge or larger creature backed up against a cliff who expects to be targeted by arrows, can they 'press themselves to the wall [...]

What you want to achieve is more cover than squeeze in my opinion and cover provide a +4 AC... and I think, in this case, is fine since the creature is acting to be protected from arrow fired at him from up the cliff so I suggest you think about "cover" more than "squeeze".
Other than this, cover gives you the chance (but is not automatic) to make Stealth checks if you want.