Marginal battery, shorting inside the starter motor or maybe insufficient earthing between engine and battery.
The starting circuit is taking ALL the power there is from the battery leaving none for sparks.
The moment the key is released there is power for the sparks and as the engine is turning it can start.
The problem is that if it doesn't go 1st time there is less power in the battery for the next start.
So things can go downhill quite quickly unless you bring the starting handle into play.
When the weather is cold the battery has less charge, the oil is thicker and the starting handle will be needed rather sooner
