We measure the ac complex resistivity in the mixed state of amorphous Mo x Si 1 - x films with different thicknesses (t). For films with t=100 and 30 nm we can determine the vortex-glass-transition (VGT) line which persists down to low temperatures (T) up to high fields (B) near the upper critical field at T=0. In the liquid phase the vortex-relaxation time (τ g ) extracted from the frequency dependence of ac resistivity follows the power-law T dependence expected by the VG theory for three dimensions (3D). For the thinner (10, 6 nm) films, both the dc resistivity and τ g follow the activated T dependence except for the very low-T region, suggestive of 2D VGT. For all of the films studied, τ g in high B shows a decreased T dependence at lower T, indicating the quantum-driven fluctuations.