Vacuum losing power

\015 My vacuum is only about 8 months old and has not seen any ”heavy” action. When I switch on it will operate for 4-5 minutes on full power, then it drops to less than half power. I have looked at the filters and they appear reasonably clean. It does not smell or appear to be hot. After leaving to rest the power will return but the same happens again..Have you any suggestions?.Thanks.\015 – Rowenta Vacuums