My car is making a strange sound, but only when it's in neutral. Just started last night?

Let me preface this with I have a very small knowledge of cars and how they work!
When my car is in neutral, it makes a rattling type sound, coming from somewhere under the hood I lifted the hood and it sounds like it's coming from the main engine area. Also, I was driving at a low speed, after I noticed the sound, and my car made a high pitched squealing noise that stopped after a couple seconds. Hasn't happened again. I don't remember if the car was in gear or not at that point.

I drive I 1996 Honda Civic LX! It eats a lot of oil, and has a couple sticky gears. Other than that I haven't experienced any issues with it in the two years I've owned it.
Please let me know if you have any idea what could be causing these strange sounds, so I can take the next steps to getting this issue taken care of!

High pitched squeals come from loose belts. Belts are most often loose because they are old and hardened. Have a mechanic look at your belts. That's free. If he says replace them, ask him to show you the signs of old age. All belts get replaced at the same time. It's just cheaper over time. Loose belts are also caused by a loose tension pulley, but rarely.