Storing car in shipping container

All UNINSULATED containers of any sort (even trucks) WILL condense moisture on the inside due to more cooling on the OUTSIDE. so the mosture condenses OUT OF THE AIR onto the cold trailer / container walls and roof, .........and then rains.

Ideas..........Yes dehumidifier, which will add SOME HEAT. They will not work below freezing unless it is a design which has means TO DEFROST just like a fridge/ freezer

HEATERS. One cheap way is to buy large wattage light bulbs and "wire up" series wired sockets, meaning, operate 120V bulbs, in pairs, in series, so each bulb is 1/2 voltage. This makes them VERY reliable and lasts longer. THEY WILL PRODUCE 1/4 the wattage "heat" in this configuration.

Another way is to do same thing with cheap electric heaters. If you can score a big long 220V baseboard, it will only draw 1/4 the wattage on 110V. Hell you could buy an 8 foot (or two of them) baseboards, and just "throw them under the car." "Let's say" an 8' is 2500W at 240V. One of them operated at 120V is a little over 300W

Make sure the container is sealed as well as you can. Consider at least some form of insulation, even thin sheet styrofoam

IF YOU CAN KEEP the interior temperature at least a few degrees warmer than ambient, moisture will not condense. If you can keep it fairly sealed, moisture will not enter as fast. If you can somewhat dehumidify, there will "in the end" be less of it.

DO NOT EVER use any form of open flame combustion heater such as an LP/ oil torpedo, or a "wick" oil heater. THEY ALL produce moisture, over and above the explosion hazard