Wish I could give you a good answer to the "why" part, and I suppose it's possible that your caffeine use was somehow keeping them at bay, but I don't think anyone knows the practical "whys" of how CH begins. I also don't know what to say about the pattern of your attacks, which is indeed unusual. As you say, your symptoms sound CHy, for sure, although 10-20 minutes is on the short side for attacks (but again, not completely unheard of).
Are the 10-20-minute attacks situations where you've been having some pain and then it ramps up and then drops down again, or are they more self-contained experiences that start and stop in the 10-20-minute period? Have you tried anything for treating them (you mention sumatriptan that you have for the migraines, but you don't say whether it's in pill form or injectable)?
Since you're new to all this, you might take a look at this "overview" file: https://clusterbusters.org/forums/topic/6213-basic-non-busting-information/