Fiesta st180 starting issue

Hey all ive scoured the internet through and through and cant find any info on this particular issue

After driving my car on a hot day then parking up, if i restart it within 10 minutes it starts to stutter on startup and can last more than 10 seconds before the starter throws out and starts properly
Problem started with 7000kms on the clock and has been here til 20.000km and still present

Anyone ever experienced this before
Ford dealers have been less than helpful and we have no lemon law here
Im not replacing any parts myself or soending money as its still under new car warranty (dealers dont know whats wrong)

Thanks in advance for any info and advice