A passive, resonant starting circuit for an electrodeless HID lamp (10) includes a starting coil (Lst) that is shielded from stray capacitances that would otherwise result in detuning the resonant circuit and hence decreasing efficiency. The starting circuit (40) further includes a capacitance (Csts) coupled in series with the starting coil (Lst) and another capacitance (Cstp) coupled in parallel with the coil (Lst). In a preferred embodiment, the starting coil (Lst) is enclosed in a conductive cylindrical housing (42) which functions as both a shield from external capacitances and the resonant capacitance in parallel with the starting coil (Lst). The housing (42) has a lengthwise gap (44) in order to prevent the housing (42) from acting as a short circuit secondary with respect to the starting coil (Lst). A conductive disk (46) is mounted to the ground end of the housing (42) to increase shielding even further. The parallel resonant capacitance is determined by the length of the housing (42) and the distance between the coil (Lst) and the housing (42).