I get the "shiver" all the time - maybe even a couple of times in a day. Lexus service guy said that it was the thermo fan kicking in (which means more load on the alternator, making the revs drop momentarily).
BUT - my revs drop all the way down to almost 500 rpm, which is basically stalling the engine, and results in quite a pronounced shaking action making the whole car shiver.
The odd part is that it pretty much only happens at two points in time:
1) Straight away after I've braked to a full stop, but braking a little more firmly than usual. (Not HARD braking by the way, but a bit more than average)
2) OR, several seconds after I've come to a stop, after braking as above.
It "feels" like a fuel starvation issue - you know, fuel slopping around the tank and not being picked up by the fuel pump - but that shouldn't be possible with modern fuel systems, and regardless, happens to me even with a full tank.