Numerical simulations of initially homogenously polarized Gaussian light beam self-focusing in isotropic phase of nematic liquid crystal, the temperature of which is close to the temperature of nematic-isotropic phase transition, were carried out. Here, we show that light polarization singularities (C-lines) of both polarization handednesses are nucleated near these transversal cross-sections of the beam, in which local extrema of peak intensities of corresponding circularly polarized components of the beam are attained. These lines are closed loops, surrounding the beam axis. They appear in wide range of beam and nonlinear medium parameters. Minor fluctuations of beam polarization and amplitude profiles do not destroy these singularities.