I have lived in my apartment for a couple of months now and this is the first time this has happened. I was sitting here working and suddenly I hear a lot of loud gurgling noises coming from the toilet in the bathroom. It sounded like some kind of big animal was drowning in the toilet, so I went in, terrified at what I would find. The toilet looked normal (the gurglling had stopped), but the water level was pretty low.
I was freaked out, so I made sure the lid was closed and went to look up info on plumbing. Two minutes later I hear noise in the bathroom again, and this time it is the sound of gushing water. When the noise had stopped (after 20-30 seconds) I went in and lifted the lid and saw that the bowl was full to the normal level again and there was water all over the inside of the lid- as if it had come shooting out (good thing I closed the lid!! ). And now there is a sulfer smell in my bathroom (sewer gas? ) so the windows are open.
I flushed the toilet and it flushed normally.
What the heck is going on! Now I am worried about dying in my sleep from sewer gas asphixiation and afraid to turn on the stove (which is a gas stove).

I was not using any other plumbing went his happened (ie no washer, sink, shower, etc) but perhaps my landlords (who live upstairs) did...

Sounds to me that there is a partial blockage in the main drain downstream of your toilet. When someone upstairs flushes, the water can't immediately pass the block and water and air backs up into your toilet. You might ask the manager to have a plumber check this out.

Hopefully, Speedball will be along to confirm (or refute) this.