Octavia Starting Problem

My 2000 Octavia GLXi 1.6 is having an intermittent starting problem. I go to start and it doesn't - eventually starts after a minute but doesn't sound like it's firing fullly and doesn't run at full power and not driveable.

If I stop and start the car again 5 or 6 times it splutters a little and after one or two more goes it starts up fine - this is only happening maybe once a fortnight but I'm worried as I want to sell it soon.

I brought it to the dealer I bought it from (a Seat main dealer) he ran a VAG check and nothing showed up he cleaned the throttle body too. That evening I went to start and the same thing happened!

Any thoughts?