TIPwEIGhT,
If you are worried about the vibrations have an engineer to check up the track and balance of the M/R and the T/R, and also the balance of the fan. And if you are seriuously worried about the vibrations have the engineer to do it today.
If these actions doesn´t help have the engineers to check the "clearance" for the valves in the engine (stucked valve). We have had some times problems with valves and they might give you some indications of low frequency vibrations.
Also an overspeed can be the reason, usually indicated as vibrations thrue the cyclic due to the spindle bearings, also can be reqognised with cracks of the weldings at the fan of the engine.
But anyway, before the next flight: take your time and do a really good pre-flight, check that there is no cracks in the blades etc.
Cheers,