Is there any support contact number outside of the Garmin warranty in Brazil? I'm tired of trying to understand why my watch simply restarts when I start an activity, I've already done everything like reset and so on.
You can contact your national support through their website at https://support.garmin.com. Use the Phone or Chat options for an instant response. Email exchanges usually take a few days.
As for the rebooting at Instinct 1st gen, a frequent reason for that is the high current drawn by a defect vibration motor, so turning off the vibrations can help in many cases. A replacement is another option, but if the watch is out of warranty, it may not be easy. You can try it anyway, since it seems to be a frequent problem at this model.