having trouble not connecting to the wi-fi due to the self assigned IP address

Power cycle your router.

Your attribution of cause and effect is backward. 'Can't connect' is the problem, [being stuck with] self-assigned IP address is a symptom of the underlying problem.

Every Mac creates a self-assigned IP address when it starts up, to identify itself on the local network. A self-assigned IP address cannot be routed, so it is no good for use on the Internet.

Within a very short time, if a Router will talk to you, the self-assigned IP address is replaced by a good local IP address from your Router. This typically happens so fast, most users would swear they never had a self-assigned IP address at all.

for some reason, no Routers will give you a good local IP address.

Most obvious problems include:

too far away from Router

Trying to connect to wrong Router

bad password

Bob is correct. After updating to Catalina I had the self assigned IP address problem on my office network but not on my phone's hot spot. Rebooting office router corrected issue. Thanks Bob