i had a similar problem with my clio in november, the car would start fine now and again but most iof the time i would turn the key and whe whole car would shake! i got myself some wet start spray, unplugged the ECU
connector to the engine sprayed all the electrics and plugs and it worked - for a bit.
last month on the way to see family, i had the ipod transmitter plugged into the lighter socket. pulled up at morrisons and the car shook again, as we were doing this i pulled the ipod transmitter out and the car burst into life -
warning here is DO NOT HAVE ANY EXTRA ELECTRICALS PLUGGED INTO THE LIGHTER SOCKET ON START UP. INC SAT NAV, BATTERY CHARGERS, CIG LIGHTER (PUSHED IN) DVD PLAYERS ETC ETC
The clio has a very nsensitive electrical set up.
plug what you need in after you have started the engine.