If you have worked and paid into the system Medicare enrollment is automatic. You would already have paid for part A with your taxes. You can opt out of Part B but unless you have group coverage I would highly discourage it. Even if you currently have no health problems, if you enroll in Part B after your initial eligibility period you will have a penalty tacked on to your Part B premium that could be substantial depending on the length of time you went without Part B coverage.
Some will delay or opt out of Medicare Part B and do so without penalty.
But occasionally some will want to opt out of Medicare Part A, even though there is "no charge" for the coverage. If you opt out of Part A be aware you are putting your Social Security check at risk.
But occasionally some will want to opt out of Medicare Part A, even though there is "no charge" for the coverage. If you opt out of Part A be aware you are putting your Social Security check at risk.