How long does it take to get GPS when starting run?

From 10s to 60s depending on the days/conditions to get the green bar. But if you don't let the GPS soak for 4-5 minutes, you'll hardly get a decent track/precision, specially in running.

My experience has also been about 10-60 seconds, depending on how recently and where I last used the GPS. 10 seconds (sometimes less) if I've used the GPS near the same location in the last day or so, or up to 60 seconds if it's been weeks since I last used the GPS or it was very far away from where I'm using it now.

Soaking it for a few minutes is definitely a good idea, but honestly a lot of the time I'm impatient and just start as soon as I get the green GPS lock indication, and still get good results (just not AS good for the first few minutes, as if I had let it soak first.)

If it's regularly taking a very long time to acquire GPS, Garmin recommends sync'ing/updating the watch with Express, and then take it outside and open (but don't start) an activity, and leave it sitting outside for 30 minutes to let it build a complete satellite constellation database. Then it should acquire GPS much faster each time after that.

Thank you ALL so so much.  Very nice responses.  I will try this and see if my Aviator will speed up.  today it took about 3min to go green.  I love the tip on letting it soak in a bit!  Thank you.

Regularly syncing the watch with Garmin Connect app helps to speed up satellite acquisition time. That is because Garmin Connect uploads satellite orbits data to the watch. 

IS this not working when recording an activity?

Really?  Interesting.  I did not know this. 

From what I know, the GPS system also receives the so called "GPS almanac" (information about pre-calculated positions of satellites) from the satellites as well. So if you use the GPS watch on a very regular base (or even daily (as I do)), the signal acquisition time is most times below 5 seconds.

C.sco said:

leave it sitting outside for 30 minutes to let it build a complete satellite constellation database.

KrapfenKringel said:

IS this not working when recording an activity?

I'm sure downloading that information is done while recording an activity, on older Fenix-es. But for the Fenix 6/Forerunner 945 generation I don't know for sure, but it would be illogical if it didn't work in the same way. GPS satellites include almanac data in the signals transmitted to receivers anyway, why not use that to update the information in the watch.

https://support.garmin.com/en-US/?faq=6IbaJEHc1i9gydzQomXzyA

As noted leaving the watch outside with a  GPS activity selected for 15 mins or more is usually sufficient to refresh the data. There is no need to actually start the activity; just leave it there looking for and connecting to the satellites.

Most activities have Power Save Timeout set to normal by default. This means the watch will revert back to the watch face after 5 minutes unless the activity is started. Change the setting to Extended to extend this to 25 minutes.

This was a helpful link.  I actually just checked my watch and it says the EPO files have expired.  So, I will sync before my next run this coming week and see if I can get them updated and then see if it fixes it :-)