When you do the sped test with the app, it has three screens of different speed tests;
- Your device (phone?) to the internet
- The router to the internet (this will most likely be the fastest)
- Your device to the router (which may be slightly faster than #1)
This helps you distinguish where the slow bit is. If you haven't changed the Starlink router to have separate 2.4 and 5GHz networks, do so, and recheck the speeds using just the 5GHz network.
How old is whatever you are trying to test the network with? Have you ever seen it run faster?
More than 100Mbits/s is normal. Less than that is either momentary, or a problem with your network or device speed. You could post screenshots from each of the speed tests, if you want more help.
All the best,
Peter