This opinion is coming from someone who has been drinking Sake for three years so take it or leave it. Others have been drinking Sake longer to which I say, to each their own.
Now that we have that out of the way lets dive into whether or not you should warm your Sake before you drink it. As I write this article the fall weather is well on its way. Brisk mornings, warm afternoons, and cool nights now. This is the perfect time to heat some of your favorite Sake, sit outside in the cool temps of the evening and sip.
When heating sake you change the taste, it's that simple, sometimes it will enhance the flavor, sometimes it won't, but it will always change it. Should you make it super hot? Should you make it tepid? My humble response is to drink it how you like it. That's it. Cold Sake out of the refrigerator has its place, but there is nothing like warmed up Sake in the fall and winter months. It's the "Hot apple cider" to alcohol.
To warm Sake, all you have to do is have hot water, your open bottle and 2-3 minutes, and you are good. Some Sake's I have had gain a fruity taste after warming it up, whereas others lose their harshness and become more tasteless. So I say enjoy your Sake as you like but try it differently sometimes, you might like it.