Sounds like flame device or thermostat, etc., and you
must get a Corgi or official manufacturer engineer in. Gas appliances and indeed electrical appliances must be checked by qualified engineers. (Sorry if I sound patronising.)
Our Stoves cooker has the same problem every few years, and we always think it is the thermostat. Stoves come round to fix it, and it is sometimes the thermostat and sometimes the flame device. Sometimes, it is both!
Do as metropolis says and get the cooker checked. (Nag nag!

)
Anyway, it is OK to mention cookers because how else are we supposed to eat when watching/listening to our hi-fis/home cinema/computers/games consoles?

Also, cookers make noise and pretty sights (the gas flames or halogen hob!

), so I say they count as AV!