Scans everytime phone is turned on

The Norton setting on my Samsung Galaxy S5 is set to scan weekly but instead it scans everytime I turn the phone on (power on). It seems to have started doing this after the last software update. This takes longer than I’d like and the phone is a dog until it is finished. I tried changing the setting to never scan (as a test) but it still scans as soon as the phone is turned on… any ideas?