electrolux cyclone xl keeps stoping and starting?

hi ive got a electrolux cyclone xl and it keep's stopping and starting while im using it at first i thought it was a break in the wire so i switched it on and did not move it and it does the same if i turn the power down it lasts longer ive tried removing the polen filter and this helps i think it's a overheating problem but dont know if this model is fiitted with a thormo switch if it is it could be that as the exhaust is rather hot if there is a thermo switch where is it and how can i check it