Procrastination is widespread self-undermining behaviour that negatively impacts individual performance and well-being. Psychological research has identified a variety of factors that influence this complex behaviour. However, how these factors interact and influence procrastination is poorly understood; there is no uniform theory that integrates all these factors. This paper presents an initial conceptual model of procrastination built from factors that are found in the psychological literature. In addition, it presents a formalization of the model that will serve as the basis for a computational model. The aim of the project is to develop model-based e-coaching software that can offer personalized support to individuals in their struggle with procrastination.