To center text inside a TextFormField, use the contentPadding property of the InputDecoration class.
Example:
decoration: InputDecoration(
          counterText: counterText,
          isDense: true,
          filled: true,
        contentPadding: EdgeInsets.all(8.0),
          fillColor: Palette.textFieldBackground,
          prefixIcon: prefixIcon,
          suffixIcon: suffixIcon,
          suffixText: suffixText?.tr,
          prefixText: prefixText?.tr,
          errorText: errorText?.tr,
          hintText: hintText?.tr,
          prefixIconConstraints: prefixIconConstraints,
          border: OutlineInputBorder(
              borderSide: BorderSide.none,
              borderRadius: BorderRadius.all(Radius.circular(borderRadius))),
          errorMaxLines: 3),
By adjusting the contentPadding, you can control the vertical and horizontal positioning of the text inside the field.