Uno Wifi rev2 - after long time it disconnects
As you have not given the details there are some things to check 


is your Nina-Firmware > 1.2.4
If not update to the latest 1.3.0 via the WiFi101-FirmwareUpdater-Plugin 0.10.10 is included in the ArduinoIDE 1.8.12 or greater
Disconnect before you reconnect (in case of router drop-outs) and
Close any connection before sending/receiving. This will free the socket on the Nina module. Stop the client after doing the stuff needed with   client.stop();
If there is any server connection code in setup this should be run in a reconnect routine (as you did not include setup) just as a hint 
Make sure that after a certain period the while (status != WL_CONNECTED) and while (client.connected()) are broken and error testing takes place e.g. if (status==WL_DISCONNECTED || status==WL_CONNECTION_LOST){.. do something to change that ..}
If all fails implement a routine that checks the signal and restarts the sketch if the router has dropped out (for whatever reason).


Disconnect code:

void connectToWifi() {
    // This new line is required to disconnect the previous connection otherwise
    // it will try to use the old connection and never reconnect if the connection fails
    status = WiFi.disconnect();

    // attempt to connect to Wifi network:
    while (status != WL_CONNECTED) {
    .... REST of your code ...
    }
}


Hint (as you did not show setup) if you have something like

client.connect(server, 80);


move it to the reconnection routine in the form of 

if (client.connect(server, 80)) {
    Serial.println("connecting...");
.... REST of reconnect ...
} 


Restart code if wifi signal is lost

void(* resetFunc) (void) = 0; // Declare reset function at address 0

void loop() {
  if (WiFi.RSSI() == 0) // Checks if Wifi signal lost.
  { resetFunc(); // Calls Reset
  }
// Rest of code goes here.
}


This should altogether ensure a long and stable running client