To resolve the issue of the Mercari app freezing when selecting the shipping option, follow these steps:

1. Check for Updates:
- Ensure that you are using the latest version of the Mercari app. Go to the Google Play Store and check for any available updates.

2. Clear App Cache and Data:
- Go to your device's Settings.
- Tap on Apps or Application Manager.
- Find and select Mercari.
- Tap on Storage.
- Clear both Cache and Data. This can help fix performance issues, including freezing or crashing - learn more.

3. Restart Your Device:
- After clearing the app cache and data, restart your device. This can help refresh your system and improve app performance.

4. Check Shipping Settings:
- Open the Mercari app and go to your account settings.
- Make sure your shipping preferences are set correctly. If your shipping option is set to "local only," it may cause issues when you try to access shipping options for listings - learn more.

5. Reinstall the App:
- If the problem persists, uninstall the Mercari app from your device.
- Go to the Google Play Store and reinstall it. This can help install the latest version and remove any potential corruption in the app files.

6. Check for Background Apps:
- While using Mercari, ensure that you do not have many background apps running that could slow down your device. Close unnecessary apps before listing your items.

If after following these steps the app continues to freeze, it may be beneficial to check Mercari’s official support channels or community forums to see if other users are experiencing similar issues and if there are additional fixes being discussed - learn more.