I would like to clarify that the following answer is dependent on watching through the film's opening credits. I wasn't sure exactly how this question wanted the "first five minutes" defined. If you go according to pure clock runtime, then the first minute or so is title sequences for the various production companies involved with the making of the film. Minutes 5 through 6 and even 7 are where I believe a majority of the conflict introduction takes place.
The very first thing that audiences see is McCandless's mother jerking awake. She thinks that she heard her son calling out to her. McCandless's father tries to comfort her, and it is very clear that McCandless has caused some kind of fear, anxiety, stress, emotional hurt, and so on.
What audiences don't know at that moment is when that particular moment occurs. It could be during the time that McCandless is missing, with Billie stressed that she doesn't know where her son is. The scene also might be taking place long after her son had been found dead, involving her grief over her dead son. McCandless's wandering did cause worry and tension within his family, so there is conflict there, but I would recommend focusing on the next conflict that the film introduces to audiences.
The next conflict introduced is a much more prevalent conflict. It is a man-versus-nature conflict. After the scene breaks from Walt and Billie, audiences see amazing cinematography sequences of the Alaskan wilderness. Over those shots are words that McCandless wrote in a letter.
Audiences will finally be greeted with a shot of a lone Ford F150 driving down a snowy road. McCandless exits the passenger side of the vehicle and begins heading into the wilderness. Realizing that McCandless isn't prepared, the driver gives McCandless a better pair of boots. The driver also tells McCandless to call him if McCandless survives his time in the wilderness. It's an ominous comment, and audiences should immediately suspect that McCandless is in over his head.
The next ninety seconds or so of the film consists of a bunch of wide-angle shots that either show only wilderness or show a very small McCandless against a very rugged, harsh, and beautiful Alaskan backdrop. We see him crossing freezing cold streams and struggling to hunt small game for food. McCandless's struggle, his conflict, is against the natural elements of Alaska that will eventually kill him.