been out this morning on a good run (100 miles) and car ran like a dream.went to pop out this tea time and reversed the car out the drive and it didnt feel right (non responsive).once out the drive i put it into 1st and set off but the car wouldnt go above 1500 rpm for a 3-4 mins.then seemed to clear itself so took it out for a thrash and been fine since then......... any ideas guys as to what i should check