Can 12v dc circuit spark and start a fire?
Yes, 12V can certainly cause sparks if there is a connection that is opening and/or closing.  However, I expect you are safe:


Since you are fused, any high-current short should blow the fuse before anything bad happens.
Your 12V power supply likely has some reasonable current limit, and
It's hard to ignite wood with sparks.


If you were around a flammable gas or liquid, however, any sparks could be devastating.

Once I was stranded at night (with my malfunctioning car) on a road in the wilderness.  I had some camping gear with me, but no method to light my cookstove. I used jumper cables from the car's 12V battery to create sparks and light the stove.

I don't recommend this!  It took a while for the hair on my forearms to grow back :)



P.S. Make sure you note @Trevor's important point about strain relief in his answer.