You can go forward for Certification too soon. With start-ups, things are in a state of flux for some months or perhaps some years.  When we went forward for ISO 29990 Certification (an ISO 9001 family standard specifically for Learning Providers and since replaced by ISO 21001 certification) we were in business for four years.
We needed to wait until processes and the associated procedures had bedded in.  All startups do need to wait until that kind of stability is achieved.  After all, startups are about ‘running as hard as you can with the ball’ and not about documenting things that are liable to radical change next week!
But once you are satisfied that processes and procedures are bedded in, go for it.  You definitely won’t regret it.  Your customers, your board, your staff and your bank manager will all thank you for it.  And you’ll sleep easier in your bed knowing that your business and the satisfaction of your customers in under control.