Alarm turning on for no reason

Hello!

I'm driving the car for about a week, and this evening at some point the car's alarm started going off without an evident reason.

As far as I'm aware, there is no immobilizer for this car, as I'm just using one button on the remote to lock the car and the other to unlock, there is no more buttons.

So, when the alarm goes off, I can either press the lock button, in which case the car's lights respond somewhat, but they keep blinking and the car - beeping. If I press the unlock button, the car stops the alarm beeps, plays 4 locking/unlocking beeps (the kind I hear every time locking (once) or unlocking (twice) the car) and calms down.

As I don't touch it, it locks itself automatically after some minute or so. Then some time passes (sometimes 1 min, sometimes 6 min) and the alarm goes off again.

I can also do nothing, and it stops by itself after a half-minute or so. But it's worrying me and I bet it would annoy all the neighbours through the night too. :) Nevermind the alarm using the battery all night…

I've tried to open and close all the doors firmly, and even the bonnet, but to no avail.

I'm not sure if it is related or not, but in the last couple of days I got some alarm problem that is small in itself, but maybe it indicates to some problems that causes also this going-off thing.

Namely, when I unlocked the car, instead of beeping once to inform about being unlocked, it started beeping also the second and third time. It stopped only when I pressed the unlock button the second time. I'm not sure how long it would have continue beeping if I hadn't re-unlocked it. Now I think maybe it would just beep four times, but then I was afraid it would continue forever, so I quickly pressed unlock button.

Does anyone have any idea what could have happened and what to do? The car is kept on the street, so I cannot really leave it unlocked…

I cannot lock the car with the keys either. First of all, a lock where to put the key in is only for the front door, and only the front door gets locked when I use it.

Secondly, I thought of locking the other doors from the inside by pressing the pegs (don't know how they are called properly), which worked fine for the passenger doors, but there is no inside locking option for the boot door that I can notice. Or is there?

What do I do?