Your Apple ID locked for security reasons

its a security feature that occurs during multiple failures at login with your Apple ID. If you are seeing this, it could well possibly mean the attempts are happening on a different device. As suggested by another community member, hardening your security by providing a two step verification is key to keeping your account secure from adversaries. I suggest you do with haste. Furthermore, security questions were at a time a feasible means of security. However stepping into 2021, it's no longer adequate alone. Supplementing it with two step verification, a complex password with string of mix character, and remembering to utilize application base password managers like the Apple keychain or even third party apps like Authy are in my opinion best. Ensure you are well aware of their privacy and methodologies for their security before purchasing since all password managing apps are not made equal and you would be better off using one that uses encryption. Hope that helps along with the other recommendations stated here.

with Lief Regard,

Anthony

Someone may be trying to sign into your Apple ID. You can add 2 Factor Authentication to your account for more security. If the attempts continue, you might want to consider a name change.     

Note the restrictions in the article.

Apple ID Name Change.        

 What to do after you change your Apple ID or password - Apple Support    I suggest doing this before you change your Apple ID or password.

Apple ID -Two-factor authentication          

Two Factor Authentification availability.    

2 Factor Authentication - How to generate a recovery key

Apple ID - Using app-specific passwords.     

Apple ID - Two Step Verifications FAQ