bootlooped but dont know how to enable debugging

so this morning i woke up and my nexus 5 was in a bootloop for absolutely no reason, i have done nothing to this phone for a year and half. this happened to me once when i tried to unroot it but my device already had usb debugging on so i could just fix it from there.
so, how do i enable usb debugging on a bootlooped phone? :eek:
thanks in advance
edit: damn wrong thread section, if a mod sees this please move this to the nexus 5 section