Car cuts off while driving. What is the problem?

Hi everyone, I don't know if there is a place to introduce myself, but this is my first posting. I'm having a problem with my 2003 Toyota Rav4. It started around last year around september or october. When I started having this problem I was parked in the parking lot at school. When I tried to disarm my alarm before entering my car, I noticed that my alarm wasn't working. So I opened my door manually with my key and the alarm didn't even go off. Then I tried to start my car and it wouldn't even turn on. I looked under the hood to see if there was anything wrong with the battery. Nothing. I didn't know what was wrong. I tried to jump it and still nothing. We gave up on everything, and when I was about to call for a tow I slammed the hood down out of frustration and the alarm armed it self. I disarmed it, and the car started up again. Ok so I thought that that was really stupid, probably an alarm problem. So a few weeks go by and I'm driving on normal city roads and suddenly my car dies, shuts off. Luckily I was able to pull over about 3 lanes to the shoulder. Now I'm getting really mad, because this is starting to become really dangerous. I tried to start it up and nothing, again. I opened the hood and slammed it down, and sure enough it starts up. What the heck is going on? After that, it has happened 3 times, and I'm worried it will happen on the freeway and I won't be able to get to the shoulder fast enough. Does anyone have this same problem, or does anyone know what the problem is? What should I do? Please someone help me, this is my only form of transportation and I want to fix it before anything serious happens.

The alarm system could have a kill switch that malfunctions and shuts off you car. I would remove the alarm system and get another one. Try that. Good Luck!