I've found it varies a good bit depending on the car you select. The
Ferrari seems quite skittish, say at Monza, at least with the default setup.
Until I get used to the sim a bit, I've been running the Coventry, a bit
slower than the others, but extremely stable, and quite tossable. In online
races, I usually overtake the Ferraris and Lotus's that passed me early on,
because they've spun out somewhere :-)
Maybe try the Coventry, or even the BRM and see if that helps some. Then
maybe adjust your conrtol settings to get these fairly stable, and then try
the other cars and changing setups for them to get them stable. At least,
mostly stable :-)
Ken