A few weeks ago started having an issue with both the Road Sign Assist feature and Navigation on my 2021 GLS. Road Sign Assist will work when I first start the car, but then within a few minutes I get an error that it is not working -- first on the driver display, and then a reset message on the main console screen. At the same time, my navigation just spins and says activating. Maybe two unrelated issues but they both started at exactly the same time. Wondering if there is any relationship between the two electronically?

I do not really rely on either - i.e. use Google navigation -- so have not taken to the dealer yet. Wondering if there is something I can do to try and reset the system?

Yes, there is. The traffic sign recognition relies on contextual information from the navigation system and it doesn't work w/o it. For example the traffic signs that apply in any given situation depends on which road you are actually driving on. Highway vs. frontage road for example. The navigation data avoids the system accidentally thinking that the frontage road speed limit applies while you are driving on the highway. Similarly, the map data tells the system the prevailing speed limits, so if no speed limit sign is detected for a while it falls back to the prevailing speed limit. There are various situations where the contextual information helps resolve conflicts when multiple signs are detected.

Bring it to dealer.
Software needs to be checked and updated.