Ventura operating system loads twice on my imac

When I turn on my imac ventura 13.7.6 loads. Then screen darkens and then it loads again. Then it asks for my password and I then start using safari to do my work. Then I log out. THEN the screen goes back to the first ventura that loaded and it comes up and asks for my password....then I have to log in again. I want to backup to a hard drive but if I do am I backing up everything or just the information from the #2 loaded things? I have looked at system usage on both ...they both show the same amount of usage. Any ideas on how to have JUST ONE VENTURA LOADED?