Some phone's do appear to latch onto signal better than others @trewie , however your Samsung phone may need swapping out if under any relevant Cooling Off Period or looking at via a Samsung Experience Store or Samsung Service Centre under warranty.
Also try choosing another network in your phone's connection settings and then re choose your own network which should help to refresh your connection.
I assume as a process of elimination when you place your sim card in another phone signal is fine. So it's not the sim card or network masts at issue. i.e this happens everywhere you go ?
Daily Driver > Samsung Galaxy s²³ Ultra 512Gb in Phantom Black.
The advice I offer is my own and does not represent Samsung’s position.
I'm here to help. " This is the way. "
