My iPhone boots to the apple logo and then turns itself off

My iphone 6 has been doing this for months but before it would turn on fully so I could still use it. Now it isn't even loading past the apple logo and if it does as soon as I enter my passcode it freezes for a minute and then turns off. Its currently just loading the apple logo and then shutting off, repeatedly. I think it might be a problem with the battery.

I have a iPhone 6 it wouldn't respond after I hit the lock button and closed out my phone. I reset it by hitting the lock button and home button and held for 10 seconds and it acted as if I worked and then wouldn't power up past the Apple screen and then now it won't do nothing

My iphone 6s does this and it will stay obn the apple logo for about 30 seconds and then shut off.. Please if someone knows explain how to fix it (:

I see you've sorted your problem but for the future try this too! I had my phone on charge all night then in the morning it kept on rebooting and didn't charge at all. I do have batterie issues so I think that is the cause. When I came on sites like this everyone was saying plug it into iTunes and all that but my mac is too old to work with my iPhone 6+. Instead I simply help in the on button the whole time that the apple logo appeared on my screen and it just turned on! It hasn't rebooted since. So easy and no data lost!! Hope this helps anyone xx

Error 4013. I Sent to repair shop for a month, but they said it can’t be repaired. then i restore my iPhone 6 with ios12 and its booted up! I’m using original iphone cable, imac and latest ios 12. Hope this helps.