hi all my trusty old work horse Octavia starts first turn of the key when cold but can take 10 seconds or so of cranking to start when warm. I have checked all voltages etc everything is fine and I put a new battery on a few weeks ago.

 

is there something obvious that I am missing glow plugs etc are fine  any ideas thanks

Usual checks on battery terminal security, starter terminals, and cranking speed apply.

 

This normally makes me think of starter or solonoid insulation breaking down when the engine is hot.