iphone 6 won't turn on, apple logo and black screen.

My iphone 6 (64gb) wouldn't turn on.

It first started when I turned off my iphone because of how slow it was working and then when I tired to turn it on again it would open to the part where the Apple logo would appear and then after a few seconds the screen would go black again. I tried charging the phone overnight and then tried switching it on but it would still open and show the Apple logo but then would turn off again. I also tried the hard reset which is pressing the home and the sleep/wake button together but it would still do the same thing, Apple logo, turn off. I then tried connecting it to my laptop which turned on the phone automatically and showed the Apple logo and when I thought I fixed it, it turned off by itself again. Then I opened itunes but somehow my phone doesn't appear and it's like it's not connected and itunes wouldn't recognise it. Please help me fix this problem, the pictures and the data in phone are very important and I don't want to lose them, knowing that I haven't backed up my data, neither do I have the data on icloud. And I've been having this problem for 3 days now and I can't wait any longer.

Thank you so much,

Warm regards.