Sorry don’t understand why restarting your phone once a week is objectionable. Smart phones are little computers, just as it would be recommended to restart a Windows computer periodically, the same goes for smart phones. It clears the memory so they can worker more efficiently.
If you want to get a new phone, that is entirely up to you. Your Moto G3 might be old but other than dropping paired devices once in awhile, it works fine…Yes?
How many devices do you have paired to your phone? They usually can handle up to 7 pairs at once, but 5 is optimal.
If you decide to get a new phone, check compatibility with your car first! Please see this post, I provided links to auto manufacturers:
Another suggestion would be to buy new Bluetooth devices. My son has a cheap fitness watch that won’t maintain a connection to any phone for more than a week without rebooting. Drove me crazy, but it’s just crappy coding in the cheap fitness watch.
Your phone isn’t going to receive any new software updates to address Bluetooth connectivity. It’s either the phone or the Bluetooth device.
It could also be an app on the phone that is causing the issues.
Uninstall any non stock apps that you do not use.
Run in safe mode for a while and see if the issue happens.
Else, last resort, Factory Reset the phone and start fresh with only the stock built in apps.
As you add back on apps, one at a time, if your issue reoccurs, then it is a software issue caused by an app.