Enabling cellular definitely helps...I usually get a lock in about 10 seconds.
Install this app and make sure you get a GPS lock of better than 10m accuracy before you start your run:
https://play.google.com/store/apps/details?id=com.bravetheskies.gpstest
A quick update that is going to expose my level of knowledge as amateur but may be helpful. I did some reading as I tried to address your issue. Apparently there are a few "stages" to getting a lock. After a GPS device gets a solid lock it calculates or requests or does something to get a better sense of GPS satellites' movement going forward to make future calculations faster.
I went up to the roof of our building (though any wide open space will do), opened up Wear GPS Status (https://play.google.com/store/apps/details?id=com.bravetheskies.gpstest), and let it run on my watch for a good 10 minutes. The accuracy wasn't great throughout, but it did occasionally dip as low as 8 meters. For good measure I then opened up my run-tracking app (Ghostracer, which I recommend since it lets you play with how frequently it records your locations - https://play.google.com/store/apps/details?id=com.bravetheskies.ghostracer) and let it run for a good 10 minutes.
Since then I've been getting faster GPS locks. Anecdotally I've also been seeing a touch less "drunk squirrel" on my running maps (though it is still not nearly as smooth as my Band 2). It might be worth a try.
I would install and test via this app:
https://play.google.com/store/apps/details?id=com.bravetheskies.gpstest
If you can't get a lock with cellular on...permissions might not be set correctly (or maybe you have a lemon?). On my Urbane 2, I can get a lock on cellular in less than 10 seconds. What app are you using?