Nexus 5 dies spontaneously

[Salma El-Ghazzawi]

For the second time this week I woke up to find my phone off. Today it was plugged in and fully charged. The last time I thought its battery died although it was weird because last I checked it was 50% so it wouldn't die so quickly. It runs M 6.0.1
Any ideas on what's causing this?

 

[dpham00]

I would install battery monitor widget from the play store to see what battery percentage it is shutting off at. Be sure to enable logging