You don't have to stay frozen. But if you want to have an easy time of things, it's not a bad idea to avoid doing things that might look a lot like reaching for your gun. A relaxed cop is usually a much friendlier cop.
A guy I know, his dad was paralyzed from the waist down, lives in a care facility and shits in a bag for the rest of his life because someone joker high on whatever didn't want to be arrested.
So folks might appreciate that a cop might be tense during a traffic stop.
