Why restarting and wifi not working

I'm also facing similar issue, if my phone shutdown due to low battery. If I turn it on it's keep rebooting. At some point it load the screen after unlocking the screen. Wifi or hotspot won't work. I'm not sure for the reason when I took it to service center they said it's motherboard issue but if it really same problem. Even calling or any other services are not suppose to work rite. Service team also saying that they don't have motherboards available. I have a strong feeling that it's the issue with the software update. Many are facing same issue.