There are multiple issues that can cause this. I would suspect a faulty part. Since you have Brocken the back glass I would recommend sourcing another housing for your logic board. If you wish to keep that housing the parts that can be causing your issues are:
· Battery.
· Charge port.
· Screen.
· Front flex assembly.
· Front or rear camera.
In some rare instances a hard drop can also cause the NAND or CPU to be compromised which would end up in a costly repair.