5x5 Beeps on startup and while running
 

I have a 2003 E-250 that beeps 5x5 times on startup and every 40-60minutes whilst running.
I have no idea what it is but from some research some people mention that it is to do with an airbag system failure. My airbag light does not illuminate at all, even when initially turning the ignition to on.
Could this be the issue and if so how do I fix it?

Thanks in advance!