Shutting down when it says there is plenty of charge

My iPad 5th gen. After recharging to a full charge and I start playing a colouring game it goes black. Sometimes I am able to restart it by pressing the top left to shut it down it starts working again and says it has 100% charge but it only lasts only a few minutes and shuts off again. If I am able to restart it again it will say there is only a very small charge left maybe only 20 to 0% left which is very frustrating to say the least. I appreciate any suggestions you can give me.