Golf 3 Cold Start Problems: 75 HP VP-TD

Unfortunately, searching the forum didn't help me find an answer, so here's my question:

'A Golf3 with a 75 hp diesel engine, which has previously run trouble-free for 160,000 km, is now having difficulty starting in warm weather in France after being turned off. However, it starts without any problems after a short cooling period.'
Does anyone have any idea where the problem might be? I'm unfortunately unable to provide more specific details about the symptoms or the car because I personally can't reproduce the issue while the engine is warm and the car is in 'F' mode...