Lumia 1020 overnight freezing

[Unregistered]

After 8.1 Update phone keeps freezing overnight. Its not happening during the day. Checked most of wp phones forums for that topic but nothing what's been suggested gave me any effects. I've tried hard resetting my phone disabling the glance screen tried switching off WiFi I've no clock apps installed. Any idea what else could I try? I'm getting really annoyed with that. Especially that I have to use different alarm clock cause I can't trust my phone. Pls help....