This is partly correct. It is any act which a person wants to get closer to Allah with and the Prophet salla Allahu alaihi wa salla. Didn’t do it nor instructed us to do it.

Am I correct in saying that one definition of bidah is: Any act of worship that is restricted when there is no proof in Quran or Sunnah for that restriction or specification. Eg if a person raises their hands for dua after salah occasionally, this is fine but to believe it has to be done after each salah or it is better if it is done after salah is bidah.