Meditating In Challenging Situations

I meditated twice today and to my surprise I managed to relax into it successfully - whilst in the background kids were making so much noise and crying and the weather was hot enough to fry an egg on the pavement.

My first session was interesting. I was getting deeply relaxed and entering an altered state of consciousness when suddenly my head which was leaning slightly to my right moved involuntarily with a jolt to the center, aligning with my body. At this point my awareness was on my neck area and then for a brief moment I just remained still trying to deepen the meditation. I decided to get up and ended the session - 10 minutes had passed by.

In my second session I experienced the usual hand movements but I focused less on the movement and focused almost exlusively on my breathing. I felt an expanding sensation in my head as if an insane amount of oxygen was being pumped in - soon I was feeling like I was just my head. As I felt like I was on the verge of falling asleep I snapped out of it.

In nearly all of my meditations I experience some kind of involuntary body movement. I wonder what these movements mean. I have read somewhere that it has to do with energy and some even say it has to do with some kind of blockage.

Of course when I first started meditation I didn't always experience IBMs so I'm leaning more towards maybe it has to do with progress. The experience of it is actually quite exciting but I would like to get past it and move deeper in my meditations.