Hello @Wellbys and welcome to the community!
After Nougat, when you wake up your screen while you have notifications pending, the system will mark those notifications as read and will remove their cards and stop blinking the LED light for them (they will stay in notification area until you dismiss them, though). So when you plug your charger, your screen is activated by default.
You can change this from Settings -> Lock screen & security -> Configure notifications -> Keep notifications on lock screen -> ENABLE.
