Yes — I call this the “Writer’s Proof Dilemma” — you need samples to get hired, but you normally need to get hired to create the writing to get the samples. It’s tricky!
A blog is a great way to demonstrate expertise in a particular niche. Additionally, websites like Hubpages, InfoBarrel, Constant Content, or Medium can be great places to start getting your words out there and developing your style.
Make it a discipline to write three articles a week, and you’ll have enough samples in a couple of months. And if you can’t make that discipline? Maybe writing isn’t for you.