Generally, many adivse against doing the IR before the CPL. If you have done most of your PPL and hour building in slow, simple singles, and go straight to a multi-engie conversion and the IR, your IR training time might be less effective because you still have to get comfortable with stepping up to a faster, more complex aircraft.
The CPL provides an intermediate step with a retractable single or, potentially, a twin if you want to do that, and in the IR course you can focus on instrument flying instead of struggeling with the aircraft.
Having said that - I did the IR before the CPL, but had 350hrs TT including 50% complex including a Turbo Saratoga, and did a single engine IR, so hand no problem.