I’ve worked as a mechanic and been hit by it before… I don’t think it’s as dangerous as you’d expect from the voltage. I think both the duration of spark, and current are very low.
At one of my first jobs, the workshop foreman would sidle up beside another mechanic who was working under the bonnet, casually put his arm on their shoulder or whatever, then touch a plug. It would make the other mechanic jump, but he himself seemed impervious (well steeled more like) to the effect.