I have the same problem, even after years of playing Aurora (generally in many other games too, but here it is much more extreme). Since I am not playing any standard games most of the time (population, research speed and similar), I usually do not start with NPR too. And there is always the new better tech, so why should I build a ship now, right?
I somehow solved it (more like a band-aid waiting to burst one day due to bad luck) by at least building Jump Point Defence platforms. I use pairs and each single one can engage 3 targets at once (or focus one REALLY unlucky fellow). This way even if I stumble upon enemy, he is aggressive and I have no fleet I am in quite good position, nothing ever came through to slap me for being too naive without a fleet. Getting through a JP is generally hard if it is properly defended so that is the best force multiplier you can have.
I usually HAVE some military design ready to produce, buys me at least half a year or so. Usually shares lots of stuff with my JP bases though, so not really a great ship in general, more like mobile version of it.