I don't know when I started, but I've played plenty of air-guitar and air-drums over the years. Yes, I'm referring to the solitary act of pretending that a rock music lightning rod is at my disposal. Using my imagination, I see both of my hands playing a real guitar or a real drumset. As silly as it all sounds, I can't help but break out into action when I'm drawn to do so. If I hear a song that gets me riled up (which could be from any genre), I let loose. While it can be a fun sort of thing to do while a song is playing, I find a deeper meaning to it.
In playing a musical instrument, there is a whole lot of mental, as well as physical, concentration going on. For example, when I'm trying to learn a song from a record, I airplay along to get the parts down. Of course it's different when you try to actually play something you learned by ear, but there is greater amount of mental preparation put in to help guide the physical playing.
The interesting thing about this is that it's also rather embarassing if someone "catches" you in mid-act. I've been "caught" a few times before and while they were awkward at first, feelings smoothed out over time. I'm now to the point where I'll actually air-drum or air-guitar a short little part in public. I don't mean it as being tacky; I do it out of love for the song.
Sometimes I wonder if I should enter an air-guitar contest. While it may be fun to knock back some beers, get up on stage and let it rip, I shy away from such shenanigans. I've seen competitions where people get up and try to play like Yngwie Malmsteen with pure air. That may be fun to see, but it's definitely not the same as seeing a real guitar be ripped up and down.
Airplaying is a part of being a music fan and a musician at the same time. I recommend you use caution around where you do it, as not everyone will understand what's prompting you to do such. For those that get enjoyment out of playing music, airplaying is just something that comes with the trade.