rainbowyogi

hi everyone thought i would introduce my self to the club. i have a bmw 330d sport e90 saloon 2007. the issue I'm having has happened twice now. car drives fine,but what happens is i park up leave to go shopping etc,when i get back i put key in ignition and no lights even my remote doesnt work,leave it fifteen mins and ignition comes back and everything fine,its a weird one had battery checked terminals checked everything ok.i at my wits end now. please help