A 100% cotton shirt is comfortable but may not provide enough insulation on its own for winter. It's best used as a base layer or paired with warmer outerwear.
To prevent cotton shirts from stretching, wash them in cold water and lay them flat to dry. Avoid hanging them while wet, as this can cause the fabric to stretch.
You can tell if cotton is preshrunk by checking the label. If not specified, a wash test can reveal any shrinkage after the first wash.