central locking clicking on and off

Anyone else get this ? I don't have the rain sensitive wipers, so its not the close window when raining function. I live in London and find the doors all unlock while driving, then I can't lock them again using the button near the handbrake - a bit worrying. Sometimes all the doors lock and unlock repeatedly for a minute or two. Sometimes it works ok. This is the third fault in less than a year, 1st was couldn't open bonnet, second was oil level sensor failed - both now sorted. I am starting to think this is not a very reliable car.