Radio/tape Cd Player problems of the 2000 Chevrolet Impala

I was on my way to work and my car just shut off out of no where at a intersection, I was scared I didnt know what to do. The car behind me almost hit me because of it. I tried starting my car back up and it wouldn't roll over or make a sound and my brakes were like locked up . But all my dash lights were on and my air bag light kept blinking and my radio was working. After about 6 times trying to start my car it finally started up and the air bag light went off for like 2 minutes and came back on and my turn signal stopped working and started making a buzzing sound . Til this day if that air bag light is on my car wont start and sometimes I can put it in nuetral and it will start . Every once in a while my car will accelerate on its own and when I put it in park it sounds like my car is just going to blow up because it sounds like my foot is on the gas . I took my car to advanced auto and got a free testing on it and my starter is good and so is my battery I recently got a new one . So I dont know what it could be . But I have noticed that alot of older Impalas have this same problem because I have googled and searched online .