This is standard behaviour for all Windows Phone 7 devices and Windows Phone 8 devices (except HTC WP8 phones running GDR 3).
Given that other systems don't always exhibit this kind of behaviour, there is a lot of user generated material about this:
Feature request to enable charging while the device appears to be powered off
General discussions confirming ...
Some people say that it is better to charge the battery of any mobile
device after it is fully drained. But, this is applicable to nickel
cadmium types and when it comes to lithium ion, it is not necessary to
fully discharge the battery before charging it. This is because when
the charge reduces too much, it might cause damage to the device.
Problem is with the charger you're using. May be it's from manufactures other than your device's. It'll have different amperage and will affect your phone. You might not face any problems with charging via PC or laptop as it's current is lower as compared to normal wall chargers. Only I can say is, get a new generic charger asap.
Nowadays, on WP 8.x and 7.x when you plug in the phone, it always switches on itself and you can't turn it off.
You'll be able to charge your phone while it is switched off when you'll upgrade to Windows 10 mobile, as stated here.
A friend of mine had a Samsung Wireless Charger for his Galaxy S7 - I successfully used it with my Lumia 950 XL.
I'd suggest trying it in-store to be certain. Or, find a store that will allow you to return it if it doesn't work.
I got the same issue when i used micromax USB cable to connect with PC and samsung charger to charge my phone. Use only MS/Nokia branded usb cables and wall bricks. they're faster in charging our phone, others wont work properly.
Do the following:
2.Get external charger 2amp recommended.
3.Charge it with external charger.
4.Charge for an hour and insert back battery.
5.Check if your phones question mark gone and it can open.
6.If it is opened then try to charge with normal charger.
:) Tell me if this didn worked.
I had a similar problem with my old HTC 8s. First i thought it's a hardware issue, but after cleaning micro usb port with ear buds and replacing my usb cable the phone started to charge properly. Some devices are sensitive to dust etc. so it's good to clean those ports from time to time.
I purchased a pad called Samsung easy charge at Best Buy. It was for some Galaxies, not all, but it charges my Nokia Lumia 920 beautifully. I tried it at the store before buying. Best Buy does not deal with Windows phones so they don't sell the pads for Nokia, but this worked for me. My grandson has a Samsung Galaxy, and the charger did not work for his ...