my iphone 13 pro won't start. tried all the initial troubleshooting

If you already tried (to no avail) the steps provided in the support article that led you here, and/or provided in this other guide:--> If your iPhone won't turn on or is frozen, I suggest that you make an appointment (*) and have your device inspected at an Apple Store or AASP (Apple Authorized Service Provider) among this list:--> Apple – Location Selector. After checking it out, they'll give you all the available options.

Regards

Giulio

(*) You can do it:

• Online:--> Genius Bar Reservation and Apple Support Options - Apple;
• Contacting a local Apple Store or AASP among the list provided above;
• Using the "Apple Store" app, available and downloadable from AppStore.