Screen is turning off on its own topic

I have a slight issue with my Droid Mini. It seems, that sometimes the screen is turning off on its own when I am in a app drawer mostly. I am scrolling, or moving apps, or even doing nothing and the screen shuts down sometimes instantly.

I sort of THINK that it may be because of the light/proximity sensor. Because it is happening when I am holding my phone in a left hand, and because the top bezel is so small, I think my finger is over some sensor here.

have you noticed the same issue? Or is it normal behavior?

Thanks