Francis,
It seems that switching to a different "activity" in Garmin can reset the GPS settings. See this response from AI:
https://www.perplexity.ai/search/my-garmin-watch-has-a-good-gps-4EvYVjySSSOl4IvHiN9hBAI think most times the recovery will be quick, but I guess not always.
If this is causing problems, I'd recommend tapping 'start', some distance from the Start control location, as this will give the GPS time to settle down, in the time it takes you to get to the Start.
Peter