How to pack items that may leak liquids for lunch?

For your situation I would recommend packing the burritos individually (or 2 at once) so this does not happen. You can achieve this by using foil, plastic wrap, or bags. Alternatively, you may try putting a sheet of wax paper (or foil/plastic wrap - but remove before microwaving) between each layer of burritos.

If this does not work for you, try the following:

Here are two methods that can be used to try to preserve expected consistency:

The easiest, and most sure to actually work:

Store the components that are wet and going to leak liquid in a different container. Unfortunately, this may involve you having to build your burrito when you want to eat it, yet this is sure to prevent a soggy burrito.

To do this you can use separate containers, bags, or however you normally package a burrito. One can also purchase plastic food containers with multiple compartments specifically made for this purpose (separation of different food items). For an example, here is a product listed on Amazon.

The second way:

This isn't a long-term fix nor is it as efficient as a multi-compartment food container. One can strategically build certain food items so that they are less likely to make bread or tortillas soggy. You have to place a food item, that will not let the bread absorb the liquid as quickly, next to the bread. The best example I can give you is that when I make a BLT sandwich that I am not going to eat immediately, I place the lettuce right next to the bread instead of putting the tomato right next to the bread. The lettuce provides a barrier between the two. Like I said though, it will not be as efficient as multi-compartment food containers.

I often take burritos for lunch at work. It microwaves great and it's filling.

What I do is wrap the burrito in foil and put it in the freezer this way I can take it in a plastic bag with the container for the other ingredients of the meal (rice,salad,etc')

I found putting the burritos in the freezer overnight and then putting them in the fridge at work preserves them in nearly perfect condition since by the time I get to eat them they are 90% thawed.

I usually do this with chicken and beef but I suppose it won't hurt the shrimp too badly either.

Shrimp, especially pre-cooked ones you get from most supermarkets, are full of water so they are the most likely culprit. The only sure-fire way to avoid a soggy burrito is to avoid ingredients that may make them soggy, this limits the list of ingredients somewhat but there's still loads to chose from. Otherwise you will have to pack the ingredients separately and put it all together before eating, which is a bit of a pain if all you want is a grab and go meal.

Alternatively you could put in ingredients what will absorb moisture. Anything dried like fruits (tomatoes included), dessicated coconut, or freeze-dried anything will absorb a bit. Whether that's the flavor you want is another story.