not sure exactly but a similar thing happened to me. Took my renault laguna to a local garage and requested an Autotune. This only costs about £25 and they run a complete electrical diagnostic check- electrics normally being the problem in lagunas. Turned out the crank sensor (which sparks the ignition) was not working properly in the cold and needed replacing. may not be wot is wrong with yours but may well unearth the real problem.
sara
November 2007