the solution that worked for me
My Samsung HT-5400 was turning really hot. I don't know if it was overheating because it did not always shut down but it was randomly opening the disk tray.
I found on Samsung's web page that there is one firmware update and another file that fixes something that has to do with the units fan. I tried this one first and no more getting hot and no more opening and closing of the tray.
Samsung support couldn't tell me this.