Managing personal Outlook.com account settings, security, and privacy
Hello Alexandra ,
My name is Jackson and thank you for your question.
I sincerely apologize for the issue you experience with your account, I am a user myself and understand how frustrating this is.
From your issue description it is possible the Microsoft security system is detecting suspicious sign in activities in your account hereby prompting you to change your account password.
You can see when and where your account has been accessed including successful sign-ins, devices used, IP address and security challenges on the Recent activity page;
https://account.live.com/activity
I will suggest you try out the Microsoft authenticator app option. The Microsoft Authenticator phone app not only adds another security layer to your Microsoft account, but it also lets you sign in to your account from your phone without a password but You’ll use a fingerprint, face recognition, or a PIN for security.
See details to set up and use the authenticator app in the link below;
https://support.microsoft.com/account-billing/9783c865-0308-42fb-a519-8cf666fe0acc
Warm regards,
Jackson E.