my HTC onex+ was getting hot quickly, then is not turning on

[AC Question]

the phone is only 6/7 months old and was working fine. but then it started getting hot for 5/6 days and now last 5 days it is not turning on. Charging light shows red and within 20 minutes change to green but then showing lock screen and fully off (whereas earlier it was taking more than 3 hours to show green !! ).
Can anyone help me PLEASE.

 

[belodion]

Does it get hot in use, or only when charging?