For portable soldering irons, here are 2 I've used.
I've had the Weller for years. It's ok, runs on butane, has it's on striker, sometimes the wind blows the flame out. Consider it reliable. Takes a while for the iron to get hot. Weller has several with various prices.
Weller P2C Butane Soldering Iron
Amazon.com: Weller P2C Butane Soldering Iron: Home Improvement
Recently bought this one and impressed with it. Runs on batteries. Note the runtime on batteries however. Heats up really fast. I like it over the Weller, but have only used it for a short time.
Hakko FX-901
Amazon.com: Hakko FX-901 Cordless Soldering Gun w/ T11-B Tip: Home Improvement
For bench, I have one of these. It is nice and I use it a lot. Have a lot of different tips for various types of soldering. I don't have the digital readout (new version), just the FX888.
Hakko FX888D-23BY
Amazon.com: Hakko FX888D-23BY Digital Soldering Station FX-888D FX-888: Home Improvement
Don't have to buy from Amazon, just a quick way to show the items.
Portable irons are nice. No cords. Batteries are a pain for the Hakko if you need more runtime (unless you have spares. I use the rechargeable batteries). Butane is ok, but have had the wind blow them out. Have used my bench for auto work but unless you really need the power, then I would suggest you keep it simple and buy a Weller portable. Only drawback is butane.
Edit: don't buy a Weller "gun". Buy a real soldering iron. Something with a decent tips; tips that be changed out depending on the work. There is no "one" soldering iron that can do it all. Considering you are using it on the vehicle, portable is to be considered vs a corded soldering iron.