Mine does that and it could be a couple of things.
1- pressure bleed down. You fuel system is under pressure. Once that pressure is release and due to the overall size of the system, it may take the pump some time to get the system up to pressure requirements. The pump may also not be as strong as it once was.
2 - computer provides the ignition timing. The sensor on the flywheel may have some debri and it takes a little more time to get through the debri to know what position the motor is in
3 - the ignition system works through resistance. The greater the resistance, the less the strength of the ignition. Check/replace your plugs, wires, cap and rotor. I had a distributor gear that had lots of play and I couldn't get it to start. Replaced the distributor and I was on my way. Been that way for over 3 years.
4 - Throttle-body is the air inlet to the engine. It has several sensors on it which will grud up. These sensors help 'idle' the engine.