Whenever I press the lock button on my iPhone, it turns off immediately after I press it. Normally, I have to press the lock button and only after I release the lock button on my iPhone 5s will it lock. now it turns off once I touch lock button

I Have an iPhone 5s running on iOS 9.3.2. i got to China yesterday and I recently connected my phone to the internet here this morning. my phone was working completely fine in the morning. I took my phone out for a short walk around the neighborhood and when I got back this problem arose:

if I so much as tap the lock button on my phone, it instantly restarts. it first turns off without the little white circular lines, and a short while later I see the white screen with the black apple logo. i do not even need to hold and release the lock button. the moment I press it, what I said above happens. Sometimes he white screen never goes to my lock screen and just stays on the white screen. If I press the lock button while on the white screen, it resarts and the white screen reappears shortly after I release the lock button. I tried updating my iPhone software from iOS 9.3.1 to 9.3.2 and nothing changer. i also tried changing the not bold text to bold text and back to reset the phone. nothing changed. Then I tried reset all settings from general-reset and nothing still changed. I am still in China connected to wifi as I write this and I would love to have this problem fixed. Thank you for your help.