There could be a less nefarious explanation for what's going on. Of course, the truth probably lies somewhere in the middle.
When learning about or getting up to speed in some topic X, there are usually many "pathways" one can take. There may be hundreds of research papers and dozens of review papers about topic X, and one doesn't need to read all of them to get an understanding of X (indeed, one would not have time to read all the papers).
It's a normal course of action to read a particular paper, and then to continue to other papers cited by that paper, or search for other papers by the same authors, etc. So when an author (or group) embarks on a research project about X, during the background research phase, they may well unintentionally end up reading lots papers by a particular author or authors, papers from particular institutions, papers about a particular sub-field of X, etc. And then, when they write their paper, this bias will carry over to their citation choices.
It's entirely possible that this is what happened here. Maybe the authors of this paper you are reviewing read a paper of yours, and then through the natural course of conducting background research, ended up reading many papers of yours. And then they suggested you as a referee, because by now they were well aware of your name, from reading so many of your papers! It's entirely possible that all this happened subconsciously (at least to some degree).
The bias towards a particular journal is harder to explain, especially since nowadays literature searching is done via inter-journal means (e.g google, arxiv), but this may be field-dependent. (In my research area, nobody ever searches for articles on the website of a particular journal, but maybe that is the norm in some fields)