2002 Skoda Octavia have skoda octavia 1.9tdi 2002 mark 1, yellow coiled glow plug lights is constant on engine doesn't fire although cranks well can anyone help me here.tia

I insert the key into ignition switch turns it on all the lights turns up and gets off accept glow plug light and the engine doesn't fire although cranking is good,after several attempts with key turning ON and OFF some time the light automatically turns off and vehicle starts.whats will be issue,how can it be resolved