Front end shimmy

[Nash]

My 98 Z71 has developed a shimmy in the front end. It seems to happen around 35 to 45 MPH. I recently rotated the tires. I did the work myself, and made sure everything was lined up correctly and the lug nuts torqued to spec. I did the rotation because I noticed the front tires were getting wear on the outer edges. Both sides had about the same wear. I probably need a front end alignment, but would that cause the front end to shimmy? Should I check any other front end parts for wear? I guess it could be a tire out of balance, but I didn't notice a problem with the back tires before I rotated them. Any help would be appreciated.

[Nice rig]

Sounds like the classic wheel out of balance. Take it in and get the wheels re-balanced and you should be good to go.