One problem related to software has been reported for the 2005 Toyota Sienna. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2005 Toyota Sienna based on all problems reported for the 2005 Sienna.
After I read the article about apple inc. Co-founder steve "woz" wozniak's experience about his 2010 prius, I was relieved somewhat from my own doubt and confusion. I bought a used 2005 Sienna xle limited (with radar sensor) last November with 95000 mileage. It accelerated unintentionally several times when I was using cruise control with only single push of the acceleration handle. I once let the car went up to 90 mph before I braked it off from the cruise control mode. The acceleration was very powerful when it malfunctioned. All happened in several seconds. You could hear the engine revering loudly towards full speed. I had no problem to brake it off every time though. I also believe it is an electronic or software problem since none of my feet was on any pedal when this happened and there was no floor mat issue at all.