There are two components to warming corn tortillas. One is adding heat. The other is adding moisture.
The easiest and quickest way to warm corn tortillas is in the microwave. It's a small space that can be easily turned into a sauna for them.
I brush a tiny bit of water on the tortilla. Just one little swipe is all you need. Stack the tortillas on a plate and cover with wax paper.
Heat the tortillas for about a minute, take them out and immediately flip them over. This keeps the one on the bottom from getting too soft.