[frukt]

Well, first of all we need to understand why is it happening? There are 2 reasons, let's look at what are they!

1 - Software

2 - Hardware

Now it could be cause of recent software update that you have installed so in that case what you can do is - save all the data to your computer and format the phone to see if has resolved the issue most probably it will if it is a software issue

Another thing is that the auto re-start option is turned On. So turn it off - Go to settings then on the search bar type auto re-start after you do that click on it to turn it off.

if none of the above works for you so it is probably a hardware issue for which you'd have to visit the service centre!

hope this helps ��