Question

For some reason my dashboard will only allow me a few seconds before expiring the session. All I changed was the WordPress URL setting in General Settings.

Answer

Login Sessions are timed by cookies in your browser.. when the cookie expires then you get logged out.

The first thing that you should do is check your browser by closing the window to your site and clearing the browser cache. Then close your browser and restart. Login normally and see if the problem goes away.

The second thing is you should make sure that the
SiteURL and the WordPress Location URL are the same or similar

What you are looking for is the subdomain
if one says www.yoursite.com and the other says yoursite.com make them the same

another problem could be a browser plugin that blocks cookies or a setting or even antivirus could be blocking the cookie

You may want to test another browser if you have a second one installed.