My ipad volume keeps sticking on maximum volume

I like to keep my iPad on mute but very occasionally it decides to turn itself up to maximum volume and stay there, no matter what I try. It will allow me to pull the volume back down but as soon as I lift my finger it sets off up again. The only solution is to turn the iPad off and it behaves OK when I turn it back on. Till the next time. Does anyone know how to stop it from happening? Or if I’m inadvertently doing something?