Measuring the quality factor RLC circuit
It looks to me like the second circuit that resonates around 16 MHz has a Q of about 95000 and a 3 dB bandwidth of 166 Hz. The frequency resolution (step size) of your simulation needs to be smaller then that. Usually I zoom  way in to see a high Q resonance by setting the limits of the AC analysis to be say 100-500 KHz either side of resonance