Alarm missed, sometime call, sleep of death? My phone is not waking up

Hi,

I have an alcatel 5.5 with android 5.0.2 build LRX22G unroot. And times to times I missed my call because my phone take too long time waking up.
And more important, my alarm doesn't ring and I have a "alarm missed" notification. I also notice that time to time my clock on lockscreen take multiple seconde to update when I wake up the phone.
I'm thinking maybe I have a sort of sleep of death problem, my phone take too much time to wake up from deep sleep or not wake up at all. This morning I was awake before my 7am alarm, I don't touch my phone and the alarm ring only once 30min after and shutdown by itself.

Do you have any idea how I can resolved this ?
Thanks

Alarm freezing and causing whole phone to freeze in 5.1.1 b830!!! Freaking annoying

Does anybody faces same fkin problem sht ?
This fkin really going on my freaking nerves !!!
Why the fcuk there is problem with alarm ? I just tested it and screen goes black and there is no any sound for alarm and phone half freezes I have to go to settings apps and force close fking clock app
How can I fix this crap ?