Thanks Borzki and Mariog.

As per my understanding,
for the modal analysis system's restraints are considered from static analysis ( Eg Liftoff supports will not be considered in modal analysis).
In operating cases, the snubber remains inactive as it allows thermal movement. However, in modal analysis (operating case) the snubber considered as restraint even if it is inactive in operating cases. can anyone tell me the reason behind this?

Mr. Borzki and Mr.Mariog. do you recommend using Snubber in the system to increase the system frequency?