2006 Vauxhall Corsa electric

I bought my vauxhall Corsa 1.2 2006 hatchback in October 2013 from a private seller with about 62k miles. MOT passed with no problems what so ever, and it's a decent car but a week or two after driving it, seemed mostly when I go over a drain or a pot hole that electric cuts out meaning my radio turns off, ABS and EPS light up on my dashboard but my car still has power and still drives and after a second or two everything is fine again, most of the time there is no affect to my brakes or steering but one or two times it's happened and my electric power steering stops and my steering wheel goes really hard for a split second and back to normal and the same with my brakes, hope you can help thanks