05 ford mondeo glow plug light only flashing when engine hot

[Kev winterson]

Hi all was just after some advice my mondeo starts and runs fine from cold but once it's up to temp and I switch it off if I go to start it again it's a bit lumpy and my glow plug light flashes it doesn't matter if I switch it off and back on again it doesn't fix it. The only thing is to let it cool down and then it starts and runs fine again? Any ideas muchly appreciated. 

[pragmatix]

Cam sensor