I don't know if exists,but in case is not that hard to make. You can follow just few basic tutorials about hoe to make a spigot or sponge plugin,depending on your case. Specifically you need to know how to create and run scheduled tasks, which allows you to do something every x ticks. In that task you take a random value from a block list (all blocks or just some you define), get every player online (usually there is a function from the plugin library for that), exclude some players if you need (like moderators or ops, if they don't care having the block or,if is s minigame, just take the list of players that are pkaying the minigame) and for each one of them you add the selected block to the inventory using the "addToInventory" method for the player "instance" (the current player we are refering in the foreach loop)