This paper proposes an innovative fully automatic target definition procedure to fill in the Multiple-Input Multiple-Output (MIMO) random reference matrix in cases where no information about the CSD terms is available. The developed method yields a set of coherences and phases of the CSD terms that is able to minimize the drives power needed to reach the test specifications. Additionally, the retrieved target complies with the required property of the spectral density matrix being positive semi-definite and with the constraint imposed on the PSDs, considered as test specifications. A series of tests with a three-axial electrodynamic shaker is carried out comparing the proposed target definition procedure with respect to other state-of-the-art solutions.