I received 10 phone calls from Apple security yesterday (Sunday) and wnat to know why?

Apple does not make such calls.

All such calls are scams from criminals attempting to steal your personal and financial information. The callers will often use number spoofing to pretend they are calling from a legitimate business. The correct course of action is to ignore the calls or hang up on them, repeatedly if needed. 

Avoid phishing emails, fake 'virus' alerts, phony support calls, and other scams - Apple Support

Apple does not call you. This is a scam

see this link:

Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support

There isn't a problem with your security. The calls are scams. Apple won't call you unless you called them and requested a call back.

You are welcome. Glad to help.