93 Mercury Villager Questions

2 things- sometimes when i brake (not always) the braking seems to kick in gradually, almost like anti lock breaks, you can feel it and hear it. The other more puzzling question is sometimes the whole car, but from the front end, seems to seize up when traveling between 40-50 mph. It doesn’t always happen, but the car starts to shake and almost feels like it’s going to come apart. After slowing down and/or stopping for a bit, it’s fine again.