There’s no specific time that you must wait before doing interval-style sessions, as the term ‘interval’ simply means a designated period of time or distance at which you will change the level of effort and therefore speed at which you run. It’s all about having structure.
There’s often a misconception that interval sessions are gut-wrenchingly difficult and will leave you destroyed, but this is definitely not the case. The intervals that you complete are simply the structure that makes up the larger session.
However, as you have no prior run background, it’d be sensible to build up your running experience and fitness with some steady sessions that focus on making the distances more comfortable. This may take approximately 4-6 weeks.
Once you’re happy to start, try a simple interval session that includes 5km of harder effort. Warm up as usual then include 5 x 1km efforts at RPE (rate of perceived exertion) 8, with 90secs full recovery between efforts. Then you could increase the number of reps or the distance of each interval to progress the difficulty.
If you want to focus on raw speed then start with shorter distances, maybe 6-8 x 200m, but make sure you take adequate recovery between efforts in order to maintain quality.