Take it back to the guy who did the alignment and tell him what the issue is, tell him to check;
The balance on all wheels, re-balance if required.
Check all tires, in and out and see if any walls have given way.
Check your rims, ideally have them run on the balancing machine without the rubber on and see if they turn a perfect circle (see rim from side) and in a straight line (see rim from behind).
Do the alignment again.
If all this doesn't work, put back the wheels the way they were and then check the drive.