W212 long crank when warm

[Weebob]

Hi guys. I have a 2010 e220cdi w212. When starting from cold car is perfect. If engine is warm and car sits for short time will crank over for period before it starts. Sometimes takes even second turn of key before it fires up. Thought possibly crankshaft sensor but any guidance would be appreciated

 

[Petrol Pete]

How old is the battery ? Reason I ask is an old battery can actually give problems cranking when very hot , just as it can when very cold.