In a vehicle, the supply will be 12, or sometimes 24 volts dc. There is some shock hazard, but the danger is from the amount of current available. The current from a car battery is sufficient to cause wire to explode, hurling chunks of burning metal and plastic. If you doubt your abilities in any of the above situations, try to get help. One last caution concerns the solder itself.
Solder contains a high percentage of lead.
Dispose of used solder, and desoldering braid. Keep all solder substances out of the reach of children. It is also good practice to wash your hands after handling solder. Lead poisoning can ruin a perfectly good body. If the tip, or heater barrel are in contact with metal, the iron will not get as hot as it should, as quickly as it should.