In order to setup an automatic repeating PowerPoint presentation you will need to 1) set a timer to auto advance every slide and 2) set it to loop back to the beginning slide from the final slide.
Set all slides to auto advance after a certain period of time
Go to the Transitions tab
In the Timing section, located to the far right, you may enter in a time under the Advance Slide heading
You may repeat this for each slide if you would like for them to have different display lengths or click on the Apply To All button to set all slides to the same display time
Set slideshow to repeat/loop on final slide
Go to the Slide Show tab
Click on Set Up Slide Show
Under the Show options section, enable Loop continuously until 'Esc'
If you have the slides set to auto advance, under the Advance slides section “Use timings, if present” should be the selected option
Click OK to save the changes and close this window