You are not alone. I also am afraid to start the next quilt. I guess it is because I want to really like it when I am done, and I have no real confidence in my ability to select fabric and patterns. Normally I end up liking what I have made, but not always. So, yes, I get a bit cautious about starting a new quilt. You are not alone at all.
However, your quilt plan sounds wonderful. I think that once you get one of those log cabin blocks done, you will be ready. Maybe that would help...just cut out enough fabric for a few blocks, make those, and then you will be hooked.
Good luck to you.
Dina