Yes, there is a free Turnitin checker. It is called Scribbr and it is powered by Turnitin. You can use it to check up to 500 words for free. To use it, simply go to the Scribbr website and click on the "Free Plagiarism Checker" button.
You will then be able to paste your text into the checker and it will scan it for plagiarism. The results will show you how much of your text is original and how much of it is similar to other content in the Turnitin database.