When I'm driving at highway speeds and hit the brakes hard-ish (e.g., if the car in front of me stops or if I suddenly realize I'm going too fast on an exit ramp), my 1997 Honda Accord feels like it's shimmying from side to side. It only happens for a moment, but in that moment I feel like I'm on the verge of losing control of the car. I've only noticed this in the last few months.
Any ideas what this might be? I'm going in for an oil change tomorrow and would like to ask my mechanic to take a look at this, but I'd like to have some theories/guesses in my back pocket before I go in. Thanks!