l was driving it one night and the headlights sometimes seem to be moving up and down even when the car was stationary. Any ideas?

if it has electronic adjusting headlights l would suspect faulty wiring probably bad connections !

Does it have Xenon headlamps?
If so it will have automatic height adjustment, which constantly adjusts to keep the lamps level to avoid blinding oncoming traffic. It uses sensors on the suspension for this, & will compensate for acceleration & braking (so if u ride the clutch when stationary the car will pitch slightly & the headlamps will adjust to compensate). It also defaults to the lowest position when the lamps first come on, the adjusts from there within a second or two.
However, the system can fail, which leaves the lamps ''confused'' & causes irregular adjusting. If the control system is not certain it defaults to the lowest position.
The system on my Mégane failed, & required new sensors to be fitted & a trapped wire to be replaced - which was done under warranty, so l do not know the cost.

l have a 2002 Laguna & suffered this problem for about 5 minutes until l realised my wife had put the seat forward for herself & in the new position my right knee was moving the little adjuster up and down depending if it was a right or left turn.