Worcester Greenstar 24i junior: doesn't work!?

Hi
I've just moved into a new property, the boiler is only about 2 years old; when I moved into this house the boiler was perfectly working and the previous owners used to leave it always on (they never used to switch it off, it was set on timer for both water and CH). Since I moved in (only few days) I then started switching the boiler on and off using the on/off button on the control panel depending whether I wanted it on or off. It worked fine till two days ago: it goes on but the reset button flashes red, so I press that and everything seems to start up. It only works for a minute or so and then it stops and the reset button starts to flash again and also the blue main fault indicator light flashes at regular intervals. Last night I noticed that the pressure gauge showed to be down to 0 bars so using the valve at the bottom of the boiler I made the pressure go up to 1.5 bars. Both the fault indicator and the reset button were flashing as per before increasing the water pressure & after having pressed the reset button the system unfortunately did again exactly the same as per before I increased the water pressure (it did seem it all started but it then stopped after about a minute or so). As this system was not used to be turned off and since i moved in this house I then started switching it on and off, it seems I have kind of 'shocked' the system...? Does anyone have any suggestion on what could I do myself before thinking to call an engineer, please? I haven't touched the thermostat, it all seems to be working, but in my total ignorance I am imaging that the problem might be connected with the pressure/water (or similar)... I then found that at the back of the Instruction Manual of this boiler in the "General Checks' a question that says 'Is all the air bled from the primary water system?"..one thing is unfortunately there isn't in the manual no suggestion on what to do in reply to such a problem/question, and second I don't know if there is a connection anyway between the air needing to be bled from the system of whether it could be anything else.....please help, anyone!