my centurl locking on my vauxhall astra 1998 ?

MY locking on my astra if i press the open or lock buten on my key the dors will try to open. but makes a buzzing noise the heated rear window buten lights up then go's off but if i press thiss whith car runng the dors will lock pres it agen dors will unlock please help becouse the uther day in the supermarket car park my car desided to lock its self whith me in side it and it dead locked too wich means i carnt open it from inside so i had to clime out of the window thiss has only happend once but help much needed please