I was a commercial banker for 22 years and I'm now in private real estate lending. My advice would be to start immediately. You don't know what will happen in the future or how long the process will take. If rates go up, you'll be glad you locked in now if rates go down materially, there's nothing that would prevent you from refinancing.
If you're not happy with what the terms look like, you're not under the gun of a maturity to make a decision. Do you have time to shop. You also don't wanna be messing with that in Q4. Holidays, end of year schedules, etc. all have a way of making deals take longer than necessary.