in the 737-300 simulator at high altitude (37,000 ft for example) there is very strong buffet preceding stick shaker operation.
I remember an article in the Boeing magazine about angle of attack (*). It explained that on older models the stickshaker was set a a fixed AoA. On more recent airplanes the stickshaker threshold value reduces with increasing Mach to stay ahead of Mach buffet.
Since the Mach buffet is caused by transonic effects at high Mach number, it only occurs at high altitude (see buffet onset envelope in your manuals). You don't encounter it at low altitude.
(*) Boeing AERO Magazine: Operational use of angle of attack on modern commercial jet transport airplanes