Tom is correct. you really should identify the problem before getting out in traffic, at speed.
Alignment of a bicycle frame can be 'adjusted' by setting down on the ground, grabbing ahold of the frame with your hands, and pushing here or there with your foot.
(they are kinda ez to bend, so be cautious!)
Wobble could be caused by loose bearings, (wheel, or neck), spoke mis-adjustment, or a bad tire casing with a burble in it. A blow-out at speed is NOT a fun thing!
A speed wobble can be caused by too little trail in the front fork.
Oh, and I just thought of another.... the extended-back seatposts that seem to be popular with some folks can cause poor weight distribution on the cycle which will lead to poor control authority on the front wheel and this may amplify any condition leading to a wobble.
Weight should be properly balanced, front/rear, for decent steering and braking.