GP mentioned impedance, not resistance. You won't feel anything touching the 12/24V terminals in your car because they're DC. Your skin has a high resistance, but when faced with AC, has a low impedance. This makes AC much more dangerous, as you conduct 120V AC much better than 120V DC.

Even 50mA will likely kill you, as outlined on the "death graph" as we electricians call it. This is independent of voltage.

https://upload.wikimedia.org/wikipedia/commons/7/7f/IEC_TS_6...

Blue is harmless and imperceptible, green is harmless, yellow is harmful, red is fibrillation.

Edit: This illustrates why 30mA (or less) RCD protection is common (and required) in various jurisdictions, depending on the kind of circuits you're serving.