BTIZ wrote:

GPS only computes heading from "last known position" to "current position",
if you are not walking.. the "last known and current" are the same.. there
is no heading to compute.. granted with minor errors of cheap handheld GPS
units.. the "movement" could be minor inches or parts of an inch as the GPS
computes it's position.. and that will cause a heading change..

My Garmin 295 does a good job of filtering this behavior.
I have it in the "Heading Up" mode; the map presentation does
not rotate when the airplane is sitting still.

Wonder what the OP's SNRs look like? My 295 typically shows
resolution (DOP?) of just a few feet. I have to move
the aircraft a mininum of about 10ft to get it to register
a heading change.

For example, as I taxi up to the hangar, I make a 90 deg turn in
front of the hangar door. I travel less than 20ft on the new
heading, and that is just barely enough for the 295 to register
the new heading by rotating the map...

MikeM