Assalaam alaikum warahmatullahi wabrakaatuh. My question is " Do I have to perform Instijah whenever I am going to perform wudhu ? "

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad, sallallaahu`alayhi wa sallam, is His slave and Messenger.

A person is not obligated to perform Istinjaa’ (clean himself) before every ablution, and ablution has nothing to do with Istinjaa’.

Istinjaa’ is obligatory to purify the impure place from the outside, such as urine and feces. But if you had not discharged anything that makes Istinjaa’ due, no Istinjaa’ would be required from you before ablution, even when breaking wind it is not required to perform Istinjaa’ from it. The book Al-Risaalah by Ibn Abi Zayd Al-Qayrawani (p.14) reads:

“Istinjaa’ is not something that is connected to ablution, neither in the Sunnah acts of ablution nor in its obligatory acts, and it is a matter of obligation in order to remove the impurity with it so that he does not pray with it on his body. In conclusion, Istinjaa’ is caused by discharging of the impure substance, and if it is not present, then there is no need for it”.

Allah knows best.