There are four spawn locations of the nest within the cave. If you use the tomtom addon for waypoints this macro will be helpful in finding them:
/way 70.0 29.1
/way 71.1 30.9
/way 67.6 30.7
/way 69.1 31.5
The respawn time on the nests seems to be between 1-2 hours and Razormaw Matriarch's spawn timer is about the same.