Is there any way using third party apps like Pushcut etc whereby I can send a message automatically when I arrive at a specific location. No manual intervention needed.
I think you should be able to geofence trigger a Pushcut background web request to a second device running the Pushcut automation server and have that device then automatically send a message via Shortcuts.
I used to use an app called LIFTT with IFTTT to do that sort of thing (though with a push notification service rather than SMS), but I think the developers that made it have gone off to other things now.
But it may be that there are other apps that can trigger actions in IFTTT / Integromat / Zapier / Huginn / etc. that you could use to accomplish this without the Pushcut requirement for an additional modern i*OS device.
If it could be a notification other than a message, you potentially have even more options available that Pushcut could trigger via a web API request - flashing lights, notification services, smart speaker announcement, etc.
Hope that helps.