I have an older Android Phone from Samsung (GT-S7390L), and I have been using it for some time now.
I took it on a trip, and used the 3G network for the first time (I always have some wi-fi nearby), it worked normally for some hours.
There, I tried using an open wi-fi, but it was asking me to register an e-mail, and I thought it was too bothersome and switched back to 3G while I was charging the phone... But then the phone got a white line horizontally across the screen and rebooted, when it finished rebooting, I thought it was just some weird glitch, unlocked the screen with my password, then tried to go back to the messaging app I was using (Telegram) and then it restarted again.
After that, my phone keeps restarting, but not as soon as it boots, but about half a minute later, just enough for me to unlock my screen with the password and try to do anything, like, turn off the wi-fi or something.
It looks like it uses a lot of battery when rebooting, because it always seem to lose 1% of battery at every restart, if I let it restarting for a while, it gets very hot.
It recharges normally if off. I can only turn it off by removing the battery.
It restarts even if I use the time I have before it restarts tp try to restart or shut down before it restarts (White line appears over shutdown/restart splash screen)
If it's recharging and restarts, screen also gets brighter when the white line appears.
I can get it to the menu where I can factory reset it, but I have two problems with it:
1- I need the backup files for my whatsapp, as there are some important messages I have to keep
2- I don't have the number I used to make that whatsapp anymore, so I can't put it onto another phone
If someone knows what can I do, I'd appreciate a lot;
Thanks in advance!