Short answer
Yes, a hidden, minor form. Doing worship so that people see and praise you (riya) is a major sin, and scholars call it minor shirk because it gives people a share of what is owed to Allah. Unlike major shirk it does not take a person out of Islam, but it can wipe out the reward of the deed.
Riya in worship is haram. It is shirk asghar (minor shirk), not kufr. If you began a deed for Allah and a feeling of showing off came later, the deed stands, so do not abandon it; fight the feeling. A fard prayer done with riya still discharges the duty in the Hanafi school, but its reward is lost.
The four schools agree on this.
Explanation
Scholars divide shirk into two kinds. Major shirk is worshipping something besides Allah or believing someone shares His divinity; it takes a person out of Islam and is unforgiven if not repented from (4:48). Minor shirk is a sin that falls short of that, such as riya and, in many scholars' view, swearing by other than Allah. See Tawheed, shirk and kufr.
The Prophet ﷺ said that Allah says: "I am the most free of need of partners. Whoever does a deed in which he associates someone else with Me, I leave him and his shirk" (Sahih Muslim). The Quran warns of "those who make show of their deeds" (107:6), and he described the first people judged on the Day of Resurrection: a man who fought so he would be called brave, a man who learned so he would be called a scholar, and a man who gave so he would be called generous. Each was told he got what he wanted in the world.
What riya is not:
- Feeling happy when people praise a good deed you did for Allah. The Prophet ﷺ called that "the early good news of the believer".
- Doing fard acts in public, like prayer in congregation.
- Leaving a good deed because you fear riya. That is itself a trap of Shaytan.
The cure: renew your intention, hide your voluntary deeds when you can, remember that people cannot benefit or harm you, and ask Allah for sincerity. "Whoever would hope for the meeting with his Lord, let him do righteous work and not associate in the worship of his Lord anyone" (18:110). See What counts as worship? and What is hypocrisy?
The evidence
Quran, Surah Al-Maa'un 107:6
ٱلَّذِينَ هُمْ يُرَآءُونَ ﴿٦﴾
Those who make show [of their deeds]
Condemns those who worship to be seen.
Quran, Surah Al-Kahf 18:110
قُلْ إِنَّمَآ أَنَا۠ بَشَرٌۭ مِّثْلُكُمْ يُوحَىٰٓ إِلَىَّ أَنَّمَآ إِلَٰهُكُمْ إِلَٰهٌۭ وَٰحِدٌۭ ۖ فَمَن كَانَ يَرْجُوا۟ لِقَآءَ رَبِّهِۦ فَلْيَعْمَلْ عَمَلًۭا صَٰلِحًۭا وَلَا يُشْرِكْ بِعِبَادَةِ رَبِّهِۦٓ أَحَدًۢا ﴿١١٠﴾
Say, "I am only a man like you, to whom has been revealed that your god is one God. So whoever would hope for the meeting with his Lord - let him do righteous work and not associate in the worship of his Lord anyone."
Worship must be for Allah alone.
Quran, Surah An-Nisaa 4:48
إِنَّ ٱللَّهَ لَا يَغْفِرُ أَن يُشْرَكَ بِهِۦ وَيَغْفِرُ مَا دُونَ ذَٰلِكَ لِمَن يَشَآءُ ۚ وَمَن يُشْرِكْ بِٱللَّهِ فَقَدِ ٱفْتَرَىٰٓ إِثْمًا عَظِيمًا ﴿٤٨﴾
Indeed, Allah does not forgive association with Him, but He forgives what is less than that for whom He wills. And he who associates others with Allah has certainly fabricated a tremendous sin.
Major shirk is unforgiven without repentance.
Sahih Muslim 2985
Sahih... أنا أغنى الشركاء عن الشرك من عمل عملا أشرك فيه معي غيري تركته وشركه ...
"I am the most free of need of partners. Whoever does a deed associating another with Me, I leave him and his shirk."
Calls showing off a form of shirk and shows the deed is rejected.
Sahih Muslim 1905
Sahih... إن أول الناس يقضى يوم القيامة عليه رجل استشهد ...
"The first person judged on the Day of Resurrection will be a man who was killed in battle."
The hadith of those who did great deeds to be seen.
Sahih Muslim 2642
Sahih... تلك عاجل بشرى المؤمن ...
"That is the early good news of the believer."
Being pleased by praise for a sincere deed is not riya.
Where the ruling is recorded
- Radd al-Muhtar (Ibn Abidin), Kitab al-Salah, discussion of intention and riya. States that riya does not invalidate a fard prayer but removes its reward.
- Ihya Ulum al-Din (al-Ghazali), Kitab Dhamm al-Jah wa al-Riya. Explains the kinds of riya, its signs and its cure.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.