Other wise just separate all the contents into a bowl nuke that for like a minute more. Nuke the tortilla for like 40 seconds on a paper towel , rewrap it the burrito as beat as you can or enjoy it with a fork.
Gonna need more information. By side do you mean end?
Likely your microwave doesn't have a rotating base. The electromagnetic radiation used to cook food doesnt create a static wave field that propagates the entire space of the oven. Thus a stationary item isn't being heated equally.
You can either find the hot zone for your oven or get one with a rotating base. If you have one with a rotating base then you need to flip your shit halfway through because the power of your microwave is below the recommended power to cook your frozen product, leading to uneven cooking as the mass rotates due to physics.