Spiders are regular enemies that show up somewhat often, unfortunately. Enemies don't normally respawn, so there's that at least. As far as I know, enemy locations aren't randomized and are based on difficulty level, so you could use picture based guides to see what type of enemy you'll encounter next. It might help with the element of surprise/fear of randomly encountering spiders in areas.
Looking at the wiki page for spider enemies: there are some in the tutorial cave, there's a cave later on in a location called
that you should avoid, there's a dungeon called
that you should avoid too. Both of those areas feature sidequests, but if you want to avoid spiders as much as possible, it's best to avoid those areas. While the first part of Od Nua is mandatory to advance the main plot, you don't have to fight the spider queen, just don't venture too far into the first basement floor. There are locations missing from the list there, too. I remember encountering spiders in the first town's temple, which is another mandatory location you have to go through.