I drive a 1988 Volvo 740 non-turbo that's generally in quite good shape, but recently (the last two weeks) several times I've hit a medium-sized obstacle while driving, like a speed bump, a pothole, or a railroad track, and the car suddenly loses power and dies. Each time this has happened, I have been able to immediately crank the car back up and drive along like normal, so it's not the end of the world, but I'm concerned it could be a serious problem at some point. Honestly, I didn't hit any of the bumps at unreasonable speeds, and I've taken much harder hits in the past without the car stalling. Each time, I've looked around under the hood for something obviously wrong (loose wire on battery, coil, etc.) but seen nothing unusual. Please help with some suggestions of what might be going on.