Hazard lights keep on flashing but car starts ok?

I have a 2007 Renault Clio. I left it in an airport long-stay car park for two weeks and on my return I started the car but the alarm went off with the hazard lights flashing. The engine did not stop so I was able to drive it home. After a couple of miles the alarm audio stopped and the hazards stopped flashing. Now when the car is parked the hazard lights randomly flash on their own with no (thankfully!) alarm sounding. Does anyone know how I can reset the alarm system? My car is the keyless model.