Only one testimonial, rand

Hi. I would like to show only one testimonial (no scroll), but auto change the testimonial when users refresh the page.
Is it possible to do?
I did some test, but I’m a beginner…

e.g. [testimonials heading="Testimonials" auto_scroll="yes" limit="1" order_by="rand"][testimonial width="1/3" author="John Doe #1" author_title="The boss #1"]Testimonial Content #1[/testimonial][testimonial width="1/3" author="Anna Mainardi#2" author_title="Photographer #2"]Testimonial Content #2[/testimonial][testimonial width="1/3" author="Paul Lopez#3" author_title="Teacher #3"]Testimonial Content #3[/testimonial][testimonial width="1/3" author="Giuliane De Pisu#4" author_title="Pupil #4"]Testimonial Content #4[/testimonial][/testimonials]