Ink, check your breaker panel and grounds around the house, and maybe your foundation. My best bet is it's a wooden house or maybe you have wooden floors. It's been an unusualy dry winter for many parts of our country, and in the winter the air is always dry so my best guess would be natural/seasonal wood expansion stuff going on - things are just starting to warm up, the air is getting moister, and some regions are having very wet springs or late winters to makeup for the dry winter.
I had a friend who had a one-off designed house on a hillside here in LA, the ground floor was actually on two level, one offest 1/2 a story from the other. Due to the design of the house it has this huge wood beam running its entire span above and parallel to this offset between the two floor slabs. One of these slabs was solidly planted on the bedrock, the other isnt and "floats" compared to the other. Nothing was unusual until the northridge quake, but then some liquidfaction or settling happened under the free slab. The result for the past 20-years, his roof is steadily and constanly unzipping itself along this beam (I'm guessing at least a 12x18) and this beam makes the loudest pops, cracks, and sometimes moans at least once every other day... could probabley have some fun with the place if it could happen on command during halloween.
