This is not really possible in standard PowerPoint.
In some cases you can make the whole slide loop. But only if there are no further animations to run.
To get exactly what you need the only way is to use code to modify the inbuilt animations. As you might imagine this is a little bit technical but if you want a go there's a
tutorial here. Make sure you work on a copy.
If you are totally stuck I can have a junior here do it for you but there would be a small charge for their time (probably only $15- $20) johnATSIGN pptalchemy.co.uk