Struggles to start after a while

[Grajp]

My wife has a 1 series 1.6 petrol e87 2008 with only 58k and after driving and then after a few hours it struggles to start. It starts without issue when cold or within minutes after stopping when warm but in a window of about 2 hrs plus until the next day it hesitates to start but does start and then runs fine. I've changed spark plugs, which were black, ignition could see fine with each measuring 1 ohm. Cleaned the MAF but don't think that's the issue. I've pulled the injectors and each seems fine; squirted wd40 to see whether there is a leak but all seems ok. One other thing, the start stop no longer works for the past few years where the starting issue has become progressively worse but could all of this be related, I'm thinking it's a separate issue. Can anyone advise?