250 opti xs wont start hot

[Dutch]

a friend has a 250 opti xs that wont start hot. it starts cold like it
should and idle's and runs great for any amount of time. problem is
when you shut it off for a few minutes, it wont start hot. no codes
showing, and called merc, said they never had this problem. any
ideas?
thanks,.
matt

[SSIMPALA71]

can you or he tell when this happens if its losing spark when it happens? Are the injectors still clicking while cranking? Have seen a couple of pcm's go south--but never come and go.--usually takes the ignition coil driver circuit out. does it try and start or just crank and nothing?