Body position?  Anything that gets between the headset and it's paired unit
will drastically reduce the range, where you can experience static and
dropouts.

It's possible you are passing through fields of electromagnetic
interference.  Walk past a neighbor with a HAM radio, or a hot rod goes by
with unshielded ignition wires, and you can get static.  In fact, any large
or complex machinery can do weird things with wireless devices.

However, since the static seems to go away when you stop walking, it's
possible, but unlikely, that objects around you are bouncing the signals
around, confusing the headset as it tries to figure out which signal is the
right one.

It's highly unlikely motion itself could cause any problem with bluetooth.
I don't know just how fast you walk, but if you walk fast enough to
introduce a doppler effect in radio waves, which travel at roughly the speed
of light, then you can play tag with Superman.  Anyway, as long as both
devices are traveling together, you don't have to worry about it.

I'd say it's body position.  Even your arm can block the bluetooth signal as
you swing it while walking.  If you have a bit of a gut, like me, that too
can block the signal.  I'm going to try one of those arm band phone
holsters, or maybe hang the phone around my neck.  Or, I could work out and
lose my gut.

I'll start with the arm band. heh

CS