I only opened and closed the sunroof once but later that day when hitting any bump the sunroof opened on its own. Since then I haven't touched the sunroof for fear that it may open on a cold rain day .
I'm thinking it is the switch based on some Lexus forums postings I've read:
http://www.ericthecarguy.com/kunena/...-while-driving
http://www.clublexus.com/forums/ls-3...-it-s-own.html