Search in iPhone X not working properly

I use the search option everyday for finding apps and keywords in my iPhone X. I have the iOS 12.3.1 already installed.

For the last couple of days, the system-wide search (Siri) has been way too slow to deliver results; it takes more than 30 seconds to show any result. In addition, I noticed that searching any word inside the Notes app, does not show any result. This is particularly weird since making the same search using the system-wide search option, the results related to the Notes app do appear, although after more than 30 seconds.

All my notes are stored in my iCloud account.

One more thing to consider is that I use the same iCloud account for my Notes app for my iPad Pro and my Desktop iMac. In both my iMac and iPad I use the same information and all searches work fine and quickly.

I already turned off and back on my iPhone X several times with no changes in behavior. I do not know how to hard-reset this iPhone, as it does not have a Home button. But I would love to be able to resolve this issue without having to turn it to factory settings as that means several hours of restore time. Also, in other occasions in which I have done that my more than 150 Gb of photos, songs, documents, etc., do not restore properly and I have to do much work to leave everything as before.

Any suggestions as to how I should proceed? I would greatly appreciate any advise...