IPHONE GLITCHING

Firstly, you should reset the iPhone.

Force restart iPhone - Apple Support

If that doesn’t work, you should refer to this article:

If your iPhone won't turn on or is frozen - Apple Support

And finally, if nothing works you should contact Apple Support.

Contact Apple for support and service - Apple Support

Amanda_davidson Said:

"IPHONE GLITCHING: What do I do if my iPhone won't turn back on and. when it does it turns. right back. off?????"

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Being Stuck in a Boot Loop:

Seems your iPhone is suck in a Boot Loop This typically happens when you unsuccessfully download something or an update stalls.  So, refer to my User Tip: How to Fix an iPhone in a Boot Loop - Apple Support