Jerking, brake light, and check engine

So, I've had my 94 Olds 88 for a few years now. Recently, I've been running into some problems, and have gotten some suggestions on what could be wrong.

1. Sometimes, when I accelerate from a stop or slow speed, the brake light will come on for awhile. I was told that I had air in my brake lines and they needed to be bled. I did that and it worked for awhile, but now, after about 6 months or so, it has started to come on again. I was wondering if I just need to bleed them again or if there is something wrong with my breaking system. It was also suggested that my master cylinder was going out before.

2. A recent problem has been that my engine has been jerking. Whenever I have it in drive and am at a complete stop, it will idle relatively normal, but will jerk every once in awhile. It was suggested that this could be caused by a modulator on the transmission that isn't working properly, it builds up pressure then sends a signal to the accelerator to accelerate a bit. I'm not sure how it all works, it was just a suggestion.

3. My check engine light has been coming on recently, but it doesn't seem to be in any certain situation. The only simularity is that it usually comes on when I hit my breaks, but it doesn't come on every time I hit them, just random times. When I turn my car off and then back on, it doesn't seem to come back on. For this problem, I recieved the suggestion that it could be something wrong a sensor in the exhaust that tells the engine whether it's getting enough fuel or not, not sure what exactly.

Any help would be much appreciated. Thanks.

Lots of wrong info here, first slightly low fliud can set the brake lite on or a flaky parking brake lite switch. Forget the trans modulator deal, a bad plug, coil or wire could give a stutter at idle and accelerating as well as a lot of other things, car should be scanned for the code from the check engine lite. I would suggest you seek some " professional" help with this.

I don't think that it is anything to do with the plugs, wires, or coils, I've had problems with them before so I know how my car acts in those situations. I've check my coils to make sure they are sending spark, and my wires were replaced not all that long ago. I intend to get the check engine light checked at a shop. I've discovered that most problems with my car tend to be pretty common, so I figured I'd check to see if anyone else has had them.

scan for codes first