My latest theory[1] on doing things, when not motivated:

  - do nothing, stay stably where you are.
  - let the 'reluctance' wash off a little.
  - keep doing nothing (don't get drawn away)
  - make the smallest step toward your task
  - do nothing
  - make an additional tiny steps
  - hopefully[1] steps will get easier, and bigger
  - the momentum of overcoming the lack of motivation
    and making progress will bring a little joy

[1] Obviously that's only my personal anecdotal experience, based on difficulty in doing physical exercise or learning music. Many times I didn't feel capable, aching, frustrated... Just putting myself into situation and see how things can go has been leading to regular surprises.

tl; dr : long warm up time.