I can get these too, and they can be anything. It could be something I saw in a documentary that I found interesting and I'll spend days researching it online and finding more documentary's etc. The last one of those was about potential life on other planets. Or it could just be something like a movie that I enjoyed and I'll watch it a couple of times until I know almost every word.
My current "project" is being able to send all my files between my computer, 2 phones and tablet over my home internet wirelessly, this is a short one, I've only been at it since today and am nearly done... I don't know why, it might be useful some day lol.
I'll have to find something new soon lol.