Alarm problem

I parked up tonight and 5 minutes later the alarm started, I went out and double checked all windows and doors. This happened about 4 times, I even moved the car and parked it again but that didn't help. Eventually I locked it with the key and its been OK.

Any ideas? I couldn't see a thing wrong.

 

Not sure bisco I'll check it tomorrow. It might be down as I've only done short journeys today with lights and heater on as it's quite cold here.

 

I think I found the problem, I left my mobile phone in the car all night doh! It's been fine today with no issues.
I did a battery health check and that seems fair at the moment, showing 12.2v but did drop to 11.8v with accessories on. Charging at 14.4v however the weather has been really cold here and I'm only doing 2 mile trips right now in the dark with heating and sometimes wipers on. The forecast is for a slow rise in temperature from tomorrow.

Thanks all.