problems with alarm and starting

Hi, I own a x reg Fabia1.4 16v. Mileage is not bad at around 48000 but, the alarm tends to go off at different times, sometimes can go days without going off, then suddenly beep beep beep! Any ideas? Also, had cam belt changed along with map sensor(diagnostics came back with us needing a new one but still says faulty now) and trouble starting. Will turn over once then cut out, then have to keep turning over until starts. Ideas?