I have a '99 Octavia 1.6 glxi and recently it starts fine, but occaisionally the engine will race (usually within a few minutes of starting) then stall and usually takes a few minutes before starting again.

Could it be the automatic choke or has anyone got any suggestions of what it may be?

Throttle body issue I would think.

Worth removing and cleaning out, then resetting with VAG COM.

Either that or an air leak, check your brake vacuum hoses.

FYI, the Octy doesn't have a choke in the way that carburetor cars do. What it has is a cold enrichment system, which supplies extra fuel when the engine is cold and revving low, but in a much more progressive manner.

Happening more often now, started ok yesterday, drove for about 2 minutes with no problems then engine started racing, then lost power and had a rotten egg type smell.

Managed to drive back home and will investigate the usual suspects today.

Anyone got any further theories on what they suspect it may be?

"Rotten eggs" smell is usually diagnostic of sulphur getting into the engine, normally from the fuel. Have you changed fuel brand recently?

check your electric components, it may also be a sign of something short-circuiting