I had difficulties to get the IP address from the router at the start up of the Arduino.
The following helped:
I defined the Mac Adress of the Arduino in the setup:
byte mac[] = {
0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED
};
In my router setup (TPLINK) I reserved one IP address for this MAC address.
No more problem.