Skoda Octavia engine start not start

Hi my mk 2 vrs has been acting up for about 2 months most days it starts ok but some turn it on and u get the ding and the dash shows normals lights before start but also traction control and low tyre pressure also turn off sit for 30 seconds and try to start does the same my have to do this for 5 mins then fires up and as normal put it on a computer and said faulty oil pressure switch changed it still does it and ideas any one please