Wash your shirt in warm water on a cool rinse cycle. Rinsing with warm and hot water can cause the shirt to shrink, which can worsen its stiffness.
Add 1/2 cup to 1 cup of distilled white vinegar to the washer's rinse cycle to soften the fabric. White vinegar acts as a natural fabric softener and is a mild cleanser for clothing.
Promptly remove the shirt from the washer after the rinse cycle finishes. Place the shirt in the dryer and set the dryer to tumble dry. Add a single dryer sheet to the machine to soften the shirt's fabric.
Iron the shirt without using starch. Spray water from the handheld iron to remove wrinkles without stiffening the shirt.