Why does my phone keep turning off and need to be rest to work again?

Hi, I have an iPhone 8 plus and I turn it on and load all of my stuff on. When it dies, I put it on charge as normal but it wouldn’t come back on. It got stuck on the apple logo. I then went on to reset it using iTunes and it worked but would only set up as a new iPhone as when I went to restore from a backup, it would do the normal process then go to the apple logo with a progress bar. The bar would finish and it will say press home to upgrade. I do that then it restarts. When I load as a new iPhone it works until it dies then it all starts over again. Any advice please?