Nose wheel shimmy in the C150/152 seems a perennial problem. Suggest you join the Cessna Pilot Association via their website. Known as CPA. Cost you around US$55 a year but well worth it for excellent advice. Once joined then pose your question re nose wheel shimmy. CPA will immediately give you a comprehensive list of step-by step maintenance fixes to give to your maintenance organisation. Or go into their archives and locate the shimmy fix that way.
Meanwhile make sure that you rotate at the correct speed stated in the manufacturer's Pilot Operating Handbook, and avoid touching down too fast. To be quite blunt about it, you should not be flying the aircraft if you know that nose wheel shimmy is going to occur. The aircraft is actually un-airworthy until you rectify the situation.
You can also cause serious damage to various components including engine mounts. Then in a few months time, some poor blighter may have the engine fall off - all because the owner could not be bothered to spend the money to fix the problem.
I suggest that once you have the defect looked at, that you flight test it first before taking up fare paying students. There are serious legal ramifications involved if a student gets scared fartless with the shimmering and a'shakin, and goes you for stress and trauma. It would be easy money for him, particularly if his lawyer could prove that your aircraft has had a history of the problem yet you have continued to fly it for hire and reward.