2002 Suzuki Liana cutting out

i know nothing abought cars so would appreciate any help, i have had my car in the garage, and also had green flag out on 4 seperate occasions, only to be told nothing wrong with the car, might be speck of dust on electrics. So why when i go above a certain speed do 2 lights come on on the dash board ( 1 of them being like a strike of lightening ) the car then judders and slows down eventually stopping. (Not good when in fast lane on moterway). After only a few seconds the car will restart normally, on a few occasions it has stopped a number of times over a short distance, but mainly it stops once and then continues normally once restarted. CAN ANYNOE HELP ME AND DO THEY KNOW THE COST OF PUTTING IT RIGHT.