Hello, my R48G started to suddenly reboot and it won't let me get past the part where it optimizes apps. It gets stuck for a few minutes at the end of the process and then it reboots again.

Can I somehow restore factory settings without accessing the phone itself ?

Hello,

Please try with below ways:
1. Push the power button for 5s before power up.
2. Plug in the phone, you'll see a page shows reboot, factory reset, wipe the cache.
3. Choose 'Factory reset'.