An awesome resource from Kim Cooke (@CMSHPE): "Check out this resource I created for our new District's Choice Led Health Classroom curriculums. Each day will start with an inspiration video followed by a prompt for group discussion or personal journal reflection." This awesome resource can be used in many ways: goo.gl/cvs5AP.
One option would be to use the Question feature in Google Classroom. Enter the reflection question and attach the link to the video. Be sure to consider which settings you want. Do you want your students to be able to reply to each other? (Note: students will not be able to see other student responses until they have answered the question.)
Another option would be to use Flipgrid (https://flipgrid.com/). This awesome tool which is now free for teachers allows you insert the link to the video along w/ the question. Students, then, record a video response. You can moderate the responses for appropriateness prior to posting.