Respawn Timer swings wildly

what is wrong with the respawn timer??? i have seen it as high as 18 seconds, and as low as instantly respawning. i have also seen the timer add time while counting down. how can this timer be so wildly out of control like this. i have lost several games recently due to not being able to get back out there to support the team. 18 seconds is a long time to just be sitting out.