All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
Among the types of fear that reach the point of Shirk is (what is called) the secret fear. Ibn Baaz when explaining the three Islamic principles, said:
"Fear is of three categories:
1- The secret fear ... this is when a man fears a special secret power that is not tangible. It is for this reason that the worshipers of graves believe that some people have the ability to act in the universe along with Allaah. They also believe this about idols, jinn, and so forth, and this is the major Shirk. They also believe that they have the ability to give and prevent, control the hearts, and kill souls without tangible reasons..."
Shaykh Saalih Aal Ash-Shaykh said in At-Tamheed Sharh Kitaab At-Tawheed, "The fear that is Shirk is the secret fear; that is when a person has inner fear of an entity because of what he believes that this entity has that he hopes for or fears, or because he believes that it may secretly harm him.”
As regards what you find within yourself as just a feeling of fear that does not entail worship of the thing that you fear or belief that idols or what is worshiped beside Allaah can have an effect, then this does not amount to Shirk. Shaykh Al-Fawzaan said in I’aanat Al-Mustafeed bisharh Kitaab At-Tawheed, "The secret fear, which is the fear that is accompanied with the worship of other than Allaah or abandoning what Allaah has enjoined: it means that a man fears something other than Allaah, such as idols and statues and what is worshiped other than Allaah, like graves and tombs, or fears devils and jinn and gets closer to them with what they like of committing Shirk in order to be safe from their evil. This is major Shirk that takes a person out of the fold of Islam."
Allaah knows best.