- Under Google Drive, create a new Google Apps Script (you might have to look under "More" after you click the "New" button).
- Give your project a name e.g. Random redirect
- In the Code.gs tab, delete what is there and replace with this code.
- Replace the links to the Google forms with your own :-)
- Save the project then select "Deploy as web app" from the "Publish" menu. Under "Who has access to the app" select "Anyone, even anonymous".
You should then get a "Current web app URL:" that looks something like this: https://script.google.com/macros/s/AKfycbwu_Fv8gGGbzMCqot1e1-u8TereYJ9uJVfIMw02NxNUTj9WNII/exec
You can then give people this URL (or use a URL shortener first to make it look nicer e.g. bit.ly, tiny.cc or embed it in an existing webpage), and it will randomly redirect them to one of the Google forms you've added to the code.
See http://teaching.statistics-is-awesome.org/tools/random-redirector/ for the context of this gist.