This can happen when you're running lots of addons, and have Shopkeeper's history size set to a high setting. Reduce the history size and /reloadui so Shopkeeper cuts the history size down.

OR! If you don't want to lose your history, you can try turning up the Lua memory limit. This is not supported by ZOS however!

Open your usersettings.txt file - this will be located in the same directory your Addons and SavedVariables folders are.

Find the line SET LuaMemoryLimitMB "64"

Change the "64" to any higher power of 2 (128, 256). Try 128 first, start slow! :)

Save the file, and log back in to ESO.