Question is in the title. This morning I wake up to 40 more points, on various questions that I had asked since I started using this site years ago. Yesterday I had something similar. Is the site's surfacing algorithm deciding that my questions need more exposure? If not, I suppose that I can infer that I've got either a superfan or a stalker? I am aware of some people who are trying to recruit me, and someone who was really paying attention could figure out who I am from my posts.
I can answer this from the perspective of someone who has given clumps of up-votes to users at various points in time, often for old obscure answers. As Tim correctly points out in his answer, this generally starts off either when a profile piques my interest through a good question or answer in the main thread, or simply from browsing through profiles on the ranking pages. Like most people, when I look at profiles, I usually start by looking at the user's top answers, which are always very good, but for reasons that I explain below, I then look at the last page of their answers with all the zero-vote answers.
I recall seeing a few comments on this site (sorry, can't remember where I saw them) lamenting the fact that there are many good answers to questions that receive zero votes. There are many times when a user puts in a lot of effort to give a good answer, and for one reason or another it does not get any votes. For this reason, when I'm looking at profiles, I now make the effort to skip to the end of the answer pages to look at all the answers that a user has made that have received zero votes, or only one or two votes. Often I find quite a few of these that are worthy of an up-vote, and ---voila--- the user now has a nice clump of up-votes on old obscure answers they made.
I have done this with a few users now, just owing to getting interested in an answer they wrote, and then looking at their profile page. (Sorry, I can't remember if you're one of them.) I'm not sure if that makes me a "superfan" or "stalker" of the profiles I've looked at (a touch derogatory if you ask me), but I have certainly found that users often have a treasure-trove of good answers with zero votes, or low votes, which are deserving of more recognition.
My best guess: someone found your answer that s/he liked, up-voted it, clicked your profile and found other answers s/he liked. There is no algorithm that bounces questions in clusters. What is bounced on the main site is the questions with no accepted answer and the ones that were edited (either question or answer).