How can I fix my ryobi ELT1100QFA?

I have a electric ryobi weed-trimmer,ELT1100QFA,that cuts out after a few minutes use,but is OK after a pause of say,half-an-hour. This has happened two or three times,but it has finally given up the ghost. The local repair wallah says the engine has burned out,but this does'nt ring true because burn-out is usually accompanied by excessive heat and burning smells,neither of which has occurred. I suspect the trigger mechanism,but I'm not much good at rocket science! Can anyone offer any suggestions?

B Black
September 2009