Except as otherwise provided for in this section and notwithstanding any other provision of this Part III, a court shall immediately authorize service of an earnings withholding order when: a support order or modification of support order is passed on or after April 9, 1991; a case is being enforced by a support enforcement agency; and the recipient or support enforcement agency requests service of an earnings withholding order; or the Maryland Department of Health requests service of an earnings withholding order for court ordered medical support. Except as provided in subsection (d) of this section, for all child support orders that are initially issued in the State on or after January 1, 1994, regardless of whether child support payments are in arrears, a court shall immediately authorize service of an earnings withholding order on the effective date of the order. When a court orders immediate service of an earnings withholding order on or after July 1, 1994, the court shall order payments through the State disbursement unit. A court may not authorize the immediate service of an earnings withholding order if: any party demonstrates, and the court finds, that there is good cause to not require immediate earnings withholding; or the court approves of the terms of a written agreement of the parties providing for an alternative method of payment. If the court authorizes the immediate service of an earnings withholding order, the court shall immediately cause a copy of the earnings withholding order to be served on any employer of the obligor.