Ford Mondeo trouble starting

my car has trouble starting when left over night or for a long period of time,when it starts after about a minute and i turn it off and then try again it starts straight away.i took it to main dealer twice and they put it on diagnostic machine,they did'nt find anything wrong,typacly when i took it there it started straight away.ive checked battery readings are about 12v and 14v when ticking over.it seems to worsen when its cold and i use the heating and heated seat?.ive changed ignition coil,ht leads,plugs,battery,crank sensor,and lambda sensor.ive also checked air intake temp sensor,and pipes for leaks.also when ive been driving the car for a while it seems to run like a dog especially when im in traffic i dont know if these two problem are related?i also hear a slight grinding noise while starting the car just as it fires up.

i hope some good person can help me,thanks for taking the time to read my message.
john.