That Safari has been prompting users with Keychain password request ever since 2004 and it is quite annoying. I like to use Safari on my Hackintosh because it saves me more battery than if I were to use Chrome. The annoying thing about the prompt is that it keeps repeating itself after I deny it. The sure way to avoid these annoying keychain prompts is to use Google Chrome and avoid Safari, because I have noticed that this issue is only with Safari.
You can try this”
Open Keychain Access (Applications/Utilities) Select Passwords on the left. Delete your AppleID keychain. Relaunch Safari. Try logging in.
You may also get this following annoying prompt when you try and login to your Facebook account with Safari browser. Everytime you try and type your email address to try and log into Facebook you get that annoying prompt “Safari wants to use your confidential information stored in..”