There are two types of key, one which needs to be pressed to open the doors and then pushed into the dashboard slot to start the car, or one which just needs to be in your pocket to open the doors / start the car, called "PCC" or sometimes known as "keyless". PCC keys have an information "i" button on the key. If yours has the "i" but dosn't work as keyless, the dedicated PCC battery may have run down as there are two batteries in a PCC key, the other one operates the key buttons as per normal.
As Mhon72 says, In both cases the start proceedure is automated by the car's computer modules and will do whatever is necessary regarding glow plugs etc.
HTH, Simon.