Switch IP address keeps changing?

I got a Nintendo Switch lite in the summer. I had to enter the IP address into my router so that I can get NAT TYPE A. Anyway, what I noticed is that the IP address of my switch changes. Which means that I always have to enter the IP address into the router beforehand. Why does the IP address change and what can be done about it?

To do this, I would have to go far into how DHCP servers work.

To keep it simple: In a private household there's usually a DHCP server in the router. This distributes the IP addresses in your network and assigns them again after a certain period of time.

To get around this, you can either change the setting in your router (if such a function is available) so that your switch always gets the same IP address or set your switch so that it always has a static IP address on the DHCP server inquires:

https://www.nintendo.de/...96746.html