both are similar ..
i never have this issue before , but what i encounter is

if your phone battery are fully drained , when u plug in your powerbank or charger . Device required to charge for around 20min before it can fully boot up

Hi sorry to hear. Try 2 hours then.
If not, maybe something is wrong with hardware.
All the best.

try charging the phone with other charger and vice versa, charging other phones using the same charger.. U will know will side is the problem

so apa macam for you? Any luck?

Hmm too bad. Maybe there is a loose connection between battery, this issue was present on some phones that made it randomly reboot. If youre adventurous enough you can try disassembling it and adding a small piece of paper or card below (between battery and phone housing), then check connection of the battery cable. For reference Lumia 920 disassembly.
Hi there, sorry to hear you have such an issue.
Have you tried a soft reset? (power + volume down together) for 15 seconds or until it vibrates.
If it works after that then maybe its software related.
You may try using the Windows Phone recovery tool to clean flash it.
Note : IT WILL DELETE ALL DATA, Please do a backup of your important files.
Also you must use the original cable (not some cheap or pasar malam geh, or it your phone wont be detected), if it fails to detect try a different usb slot, if it still fails, try a different computer.

All the best and keep us posted.