1997 Venture autoaccel problem

I have the following symtphoms.

My car sometimes autoaccelerates. What I mean by that is that it reaches by itself to even 60km or more without even having to push the acceleration.
Once this happen if I shift it from drive it will abruptly shake you (like somebody hit you from the back), and once put in parking the engine RPM goes skyroket (stupid car dosen't have a RPM gauge, but you can hear how the engine goes very high in turration) like I would be half the pedal to the ground. The thing is tho, that sometimes I have this problem, sometimes it's normal. Once I started the engine again in 10-20 seconds and it was normal.
All this started when I drove the car by accident with the handbrake on. (Kinda stupid story)

What could the problem be? I just don't want to go to a mechanic to throw away some money again. I did that twice and I wish I didn't.

Highly appriciated, thank you