18/4 connector for repeated plugging and unplugging?
I'm rather partial to Anderson's Powerpole connectors, which are highly durable connectors rated for thousands of mating cycles, are modular so you can assemble your own four-pole connector out of four single-pole ones, and are symmetric so there's no plug and socket, just a single connector that mates with another identical one. The contacts are crimped onto the cable, so they do fit your mechanical-connection requirement, though you would want a specialized tool for crimping them. (Powerwerx makes one, as well as a different one for the high current connectors, so you don't need to spend thousands on an official Anderson one.)
Plus they're super cheap. I've never seen another connector rated for similar voltage and current that costs anywhere near as little as these do.
I've used them before as the only affordable connector I could find for 100 amp contacts, and they worked fantastically in that role, though the larger ones do start to require a fair bit of force to connect and disconnect. Even the smallest ones (15 amp) are probably far overkill for your purposes though.
Disclaimer: I am in no way affiliated with either Anderson Power Products or Powerwerx; I've merely found their products useful enough to recommend.