Why is the IRST not centered on the Eurofighter Typhoon? Following links included in this answer, I noticed the IRST is located on the left side of the Eurofighter Typhoon. It seems that this asymmetrical location is common (Dassault Rafale, MIG 29,...).

Why is the location of this device chosen so that on side seems privileged? I see no reason to prefer one side over the other, there should be the same chance for a target to be located on one side or on the other.
The Thales UK PIRATE IRST system is located here in order to allocate space on the starboard nose for the retractable in flight refueling probe.  The port space was the only available real estate for this avionics to fit.  Other aircraft like the MiG-29 have similar restrictions in space availability.

The asymmetric location does not affect functionality; the IRST seeker head does maintain full field of view without blockage from the nose or fuselage.