
I myself have GSD's, one of which is a fully trained working dog and the youngest a bitch of 16mths whose in training.. i recently had the same problem with the bitch,i found at around the same time every night give or take 10/15mins she would really kick off, what i thought was for no reason..this went on 4 about 2weeks i use to check outside, couldnt see no-one...so i just ignored her, i never once told her off for it though..i then recently found out it was one of the neighbours coming in from work,so as previous posts have said, u may not think there is anyone/anything out there but she obviously knows better..all i do with mine now when she barks is tell her shes a good girl and thank u 4 letting me know..thats normally enough to get her to be quiet now.
Good luck with her 4 the future
Nicci