When my 94 SSEi hits normal temperature, and I turn it off, then turn it back on some minutes later it idles really bad and shakes, could that be misfiring and how can I help it?

mine does that time to time....dont know what it is could be the injectors not pushing as much fuel in or something i dont really know....i think it has to deal w/ heat problems myself...i sometimes when the car is at normal operating temp i will put my code reader on and let it retrieve codes for a while because it turns on the fans on high when its lookin for codes so that can help it cool off!