If you need to heat tortillas to keep them from breaking when making fajitas or soft tacos you can easily do it in either the microwave or the oven.
To heat them up in your oven take a stack of a dozen or so tortillas and wrap them in a damp dishtowel, then wrap it all in aluminum foil. Place in the preheated oven at 300°F and heat them up for a few minutes. Don’t use the top and bottom tortilla right away as they could be slightly damp.
To tortillas up in the microwave, again wrap them up in a stack with a damp dishtowel and microwave them for a couple of minutes until they are warm enough to prevent breaking.
Do not use tinfoil in the microwave!
Once you heat them up you can place them in a tortilla container with a lid to keep the heat in, lining it in parchment paper, or wrap them in a dry dishtowel until you need them. Why the damp dish towel? This keeps them from drying out when you heat them, especially when you are doing a large stack.