Does it happen at other locations? Or just at home? I ask because of the slim chance that someone else's transmitter could be interfering with it near your house. I'd bet the chance of this is tiny, but if it ONLY happens at home? Hmmm... At least you are under warranty. Toyota should fix it, but they might have a heck of a time reproducing it if it's truly random. Might have to leave it with them for a day and see if it does it while there.
I had a random malfunction in a Subaru WRX... Drove me crazy, and after the shop had if for three days, it FINALLY happened for them. Had it not done that, they'd have handed it back to me unchanged.