When I click twice on Toggle Quad View, it let me with an ortho-view instead of the previous 3D view, forcing me to find the viewpoint I had previously again. Is there an option to remember the viewpoint? Hitting Numpad 0 to toggle between current viewpoint and camera view works.
The Quad View is comprised of the: Top, Front, Right, Camera views. There is no way of changing this. However there is a workaround/hack for this. Since you want to always return to the same perspective viewport you can use your camera as the perspective view.
Go into your camera view
Zoom in to where you can no longer see the border of the camera. This will look you standard viewport.
In the properties panel under View enable Lock Camera to View
The camera is now locked the the viewport. So when you go between quad and perspective view it will remember where you left off.
Normally Blender starts in the "User Persp" view but as soon as you go to the quad view, Blender switches to the "User Ortho" view. You can toggle between both modes with NumPad 5 key.
More info: Perspective and Orthographic Projection