Experimental [1] and numerical studies [3, 2] of transonic flows around airfoil have shown that the shock unsteadiness (also called buffet) is altered by the laminar or turbulent state of the incoming boundary layer. By performing LES simulations and SPOD of the transonic flow around an OALT25 airfoil, Zauner et al.[2] showed more specifically the co-existence of a low-frequency buffet mode and an intermediate frequency laminar separation bubble mode. The present work aims to investigate the onset of such unsteady phenomena by conducting a global stability analysis of the transonic steady flow within a RANS framework. Towards that objective, we consider the Spalart-Allmaras model (SA- neg) as a turbulence model together with a γ transition model. The study reveals the presence of an unstable low frequency eigenmode, whose frequency and stable/unstable regions coincide very well with the low frequency buffet reported by Zauner et al.[2]. Further, performed unsteady simulations (URANS) resemble the complex dynamics of multiple shock waves and flow separation, in good agreement to the LES findings. The study will be further extended for higher Reynolds numbers to assess the accuracy of the proposed RANS global stability framework for laminar transonic buffet prediction.