iphone turns on and off repeatedly

My iphone turns off and on repeatedly. It goes from a black screen to the apple start up screen back to the black screen. About 30 minutes of doing this it will come up to my home screen and as soon as I enter my pass code it will bring up my apps and then shut down again. It looks like my main 4 apps at the bottom aren't loading.

I don't really care about the phone, I just want to get my pictures off while I can.

one question was iphone trying to install an update and now it is giving me an error because it wasn't completely installed.

My plan is to try to hook it up to my computer to download the pictures off. Other plan is to take it to apples store. Battery seems to be in good health before all this.

Thank you.