Mikebo

In the last few months my 2018 Superb Estate TDI Auto has occasionally been reluctant to start when facing uphill. Our drive is on about a 15 degree slope. This morning I had to cycle the starter button/ignition 5 times before the starter would turn the engine. Once the engine was turned over it started just fine. When the vehicle is facing downhill the car starts as it should do, on the first press of the starter button. Any ideas as to why this should be happening gratefully received. PS. The car is often left for several days between outings.