FYI I've developed an XLSForm form that can be used to effectively randomize the presented order of a group of questions, but unfortunately it involves some rather complicated XPath expression handling which, regrettably, the current javaRosa does not support. It does however run perfectly under Enketo (which uses a different XPath processor).
If you happen to be using Enketo for your data collection I would be happy to share it with you privately (but I dont want to post it to the forum until it is supported by javaRosa, and hence usable under ODK Collect).
In the mean time, if you are desparate, you can probably utilize the random sampling solution posted to the Forum by @chrissyhroberts to accomplish something. Its a bit involved, requires constructing an external cvs dataset, and not truly random, but it should provide you with a non-repeating psuedo-random sample that you could utilize to drive showing your questions in a different order.