Falls out and battery-LED shows up 4 times of Z5 compact

Dear readers,

My sony experia compact z5 has a problem. It starts up until the menu needs to show up. At that point it shuts down. When it is completely out the battery-led (red lamp in the right corner) shows up 4 times. After that the device starts again to do the same thing all over again.

This repeats itself until the battery is out.

Can someone tell me what is going on and... How to fix it?

Regards;

Stef