Recently, situated willingness to communicate (WTC) has received increasing research attention in addition to traditional quantitative studies of trait-like WTC. This article is an addition to the former but unique in two ways. First, it investigates both trait and state WTC in a classroom context and explores ways to combine the two to reach a fuller understanding of why second language (L2) learners choose (or avoid) communication at given moments. Second, it investigates the communication behavior of individuals and of the group they constitute as nested systems, with the group as context for individual performance. An interventional study was conducted in a class for English as a foreign language (EFL) with 21 students in a Japanese university. During discussion sessions in English over a semester in which Initiation--Response--Feedback (IRF) patterns were avoided to encourage students to initiate communication, qualitative data based on observations, student self-reflections, and interviews and scale-based data on trait anxiety and WTC were collected. The analyses, which focused on three selected participants, revealed how differences in the frequency of self-initiated turns emerged through the interplay of enduring characteristics, including personality and proficiency, and contextual influences such as other students' reactions and group-level talk--silence patterns.