Similar fault with the Clio, sat for a year and although it started first turn of the key, when I got to the MoT testing station all I got for my key turning efforts was a flat................... That's right, no sound!
I remembered the white wire to the solenoid, wiggled it and away she went.
Damp conditions made a high resistance connection.
The advice above is spot on, but always start with the easy stuff first, Battery lead connections, starter wire connections, earth connections, then battery output & alternator output and if all else checks out, starter itself and ignition switch.