start app on startup and click coordinate
Use an automation app, most of them has built-in support for starting various types of tethering, so it may not be necessary to automate the actual button press. But if that's the only option, it can probably also be automated with any of the following apps:


Automate
(free)
Automagic (paid)
Tasker
(paid) +
AutoInput
(7-day trial)