dryer wte86304gb no heat?

hi,we have the above dryer which has an intermitant problem of not giving out any heat on every other or so load. To overcome this we have to take the back off and press a red button which resets the fault and it then works for a while, until it goes again. This is happening more often and I really want to sort it out now! Anyone have any ideas of what to replace and where to get it from? Thanks for all your help.