My notifications keep stopping.

My notifications keep stopping.  I noticed on Saturday that I had missed a call, I checked it was connected, I checked the battery settings on my phone hadn't made it go into sleep mode, I checked the notification vibrate was on the highest setting and I checked bluetooth was on but still nothing.  I charged it on Sunday and suddenly they worked again. However last night I noticed they arn't coming through.  Battery suggests more than 50%, so do you have any other suggestions?