Waiting for motivation means letting a mood run your schedule.

Motivation is a feeling, and feelings arrive on their own timetable based on sleep, weather and whatever happened at lunch. Handing your week to something that unreliable means the work only happens on days that were already good. Action tends to produce the feeling more often than the feeling produces action.

Decide the time rather than the mood: same slot, same place, whether or not you want to. Make the starting amount small enough that wanting to is not required. You can stop after ten minutes, and most days you will not.