vw golf mk4 2003 match keeps going off?

HI all,
tonight after coming back from driving my golf mk4 2003 5 door match, the alarm keeps going off after locking the car via the remote central locking. it has been raining today heavily & i have been opening the boot a few times, but now as soon as i lock the doors via
remote CL, all the indicator lights flash about 5 seconds after locking & the alarm goes off. this happened a few times & checked all the doors & windows were locked. it was then ok for an hour or 2 then the alarm started to sound again. at the moment i've had to turn the alarm off, by leaving the drivers door unlocked... i cant leave it like this every day - any ideas / causes / solutions / things to check would be much appriciated M