Actuated furniture, such as electric adjustable sit-stand desks, helps users vary their posture and contributes to comfort and health. However, studies found that users rarely initiate height changes. Therefore, in this paper, we look into furniture that adjusts itself to the user's needs. A situated interview study indicated task-changing as an opportune moment for automatic height adjustment. We then performed a Wizard of Oz study to find the best timing for changing desk height to minimize interruption and discomfort. The results are in line with prior work on task interruption in graphical user interfaces and show that the table should change height during a task change. However, results also indicate that until users build trust in the system, they prefer actuation after a task change to experience the impact of the adjustment. Based on the results, we discuss design guidelines for interactive desks with agency.