Help! 1994 Nissan Skyline jumps forward even when in park and constantly turns off while driving.?

It used to jump forward a lot more, but I recently changed the oil filter and oil myself (the last person put the wrong type of oil filter on it, and it leaked oil like none-other) and it seemed to stop. It hasn't done it in about a month or so before today. It constantly dies's while I drive it. It seems to be in the first few minutes that it'll die, so I feel like it's not electrical. All I have to do is throw it into neutral, and try turning it back on. Sometimes, it'll take multiple attempts to turn it back on. Also, once in a while, I'll actually have to come to a complete stop, put the car in park, and then attempt turning it on from there. I was hoping somebody might have an answer to my question. Everybody out here is baffled by the problem. Thanks!