The JP server lets you play runs automatically with the orange button labelled “おまかせ” near the top right. Set your phone's screen to not automatically turn off, since auto plays through runs in real time.

In the auto settings, you'll want to check all these boxes near the bottom to tell auto to do races when you need fans and use clocks when you fail:

Auto runs won't be competitive, but they're very useful for making parents or getting event points.