Tack

Step 1: group and merge the whole drawing into one layer:

Step 2: Duplicate layer at least twice (I usually do three):

Step 3: Select one layer and then go to liquify:

Step 4: Change the liquify setting to crystallize:

Step 5: Crystallize the whole layer. You can mess around with the settings to get your desired level of squigglyness.

Step 6: Do the same for the other layers you duplicated.

Step 7: Make sure the only layers visible on your drawing are the layers you have liquified then turn on animation assist:

Step 8: Set the fps somewhere between 5-7 then press play. You can see if you went too overboard with the liquify tool here and go back and adjust if you need:

Step 9: Export as animated gif!!! You’re done! Enjoy squiggly lines:

Video (sorry if I went fast):