It is critical to determine the solar disk's radiation in Mg II lines, e.g. to evaluate the radiation incident on solar chromospheric structures such as spicules or prominences, and to comprehend the radiation emitted by these structures in these lines. The aim of this project is to investigate the spatial and temporal variability of the Mg II h&k (2803.53 and 2796.35, respectively) lines in solar observations. Additionally, we seek to derive information on the spectral features of the Mg II h&k lines in the quiet sun at the centre of the sun. We present a novel approach for automatically determining the positions of k1v, k2v, k3, k2r, and k1r, as well as h1v, h2v, h3, h2r, and h1r, in the line profiles obtained by IRIS at the quiet sun centre. In this poster, we will address the variation in the spectral characteristics of the Mg II h&k lines in the quiet sun at the sun centre.