I would take off from an airport on an IFR flight plan with autopilot enabled. I get to about 17,000ft then suddenly the nose randomly pitches up and the trim goes to +7 which then causes the aircraft to stall. Anyone know how to prevent this from hapening?

Well the short answer is to fly faster.  The pitching up will be caused by the aircraft stalling.  If you said what aircraft this happened with it would of course help you to get a more fuller answer, but the bottom line (regardless of aircraft), is insufficient speed and this is happening because either your power is too low or your rate of climb is too high.