The Altea is known to have electrical problems in a control box. I had one where the headlight came on without turning them on, although went off with ignition off. The garage said known issues. Difficult to diagnose, lighting control box. Left it when it fixed itself. Come across other people with Altea issues here. Your car is in the same period.
May be a wiring issue in the car, dampness or electronics. Pass on what it actually is. Think my Altea was dampness got into the control box which fixed itself when it dried out. Had one issue when it was completely dead to start it up. There was power. Again it fixed itself
. Used another car tgat day.
Try posting on the Leon 1 thread of here:
SEAT Leon discussion forum
www.seatcupra.net