Iphone 3G- my device wont turn on after the silver apple just goes straight off, HELP?

My phone is beside me, keep coming onto the logo automatically and just switching off. I always use my phone, I can not use it as it is doing this. I would appreciate to know what is wrong with it and also would gather information on how to fix this.

Has not been next to water.
been on charge all night- I have been doing this quite a lot but I have researched this and it has nothing to do with the battery.
I did not try to delete an App. It just turned off automatically.
Sorry my phone is not in the right category. It didn't have one for phones.

Leave it to die of battery then Charge it

Try to force restart the device. And then let it drain the battery and re-charge the device. If the device still won't turn on, I guess you must restore your device via iTunes. But there is a better tool - TunesKit iOS System Recovery which can avoid data loss.
https://www.tuneskit.com/ios-system-recovery-for-mac.html