Starting Problem

[sydneycity]

Hello I have a 99 Lexus is200

When I try to start it it turns over for 4-5-10 seconds before it actually fires. Engine runs smooth and 100% percent once started but the initial time it takes to kick over isn't right. Please help

I have connected the diagnostic computer and everything is fine.

Changed plugs/ leads and air filter as well as new tank of petrol. Battery 100% ,

Still same problem. Taking 5-10 seconds to actually fire over.

Any idea why this is happening. My mechanics stumped. Maybe fuel filter or pump? But computer says that's fine..

[ilv1004s]

coudl be many things fuel pump

dirty fuel

starter motor on it's way out

low battery charge etc