From The Document Foundation Wiki
How do I automatically start an animation without the need to click
To start an animation automatically when a slide is displayed, or following a previous effect:
- select the object you want to animate
- in the sidebar, select the Animation deck
- insert the animation:
- click on the Add Effect button,
- select the animation, choosing its category, name and speed
- confirm with OK.
- For Start, select After previous
- Use the Duration control to choose the duration of the effect (if applicable)
- Use the Delay control to increase the length of the pause before the start of the effect.