why did my watch start lighting up in the middle of the night when it hadnt before?

iI have the Vivomove Trend & it just started lighting display in the middle of the night upon gesture (during my sleep time) last night. 

It has never done this before. On prior nights, gesturing did nothing which is what I want.

When ever I moved my arm, it lit up and woke me up. This is terrible. 

I checked the settings and nothing changed.

How do I make it stop?