Why does Nexus 5 goes into boot loop?

Nexus 5 goes into boot loop unless we keep pressing power button, has anyone found the exact cause and solution for this?

Phone initiates boot, google logo flashes and then it shuts down.

But it will start and even keep working till the time you are continuously pressing power button.

If you put it on charging, boot loop will continue.

Please share the exact cause and solution.