How long before you start to see results?

A recent study suggests that it will take about 66 days for an activity to become a habit. 

Been working out for a few weeks and not sure that you see a difference yet? You'll start to see a difference soon. On average when adding exercise to your weekly routine it takes about 4-8 weeks to begin to see results. They might be small differences at first, but the longer you stick with it the more noticeable they'll become.

Regularity is key to seeing results. Exercising on and off for a couple of weeks won't give you the results you are looking for–aim for 3 (or more) workouts a week, and give yourself the time for this to come a habit. 

Keep challenging yourself, increase your reps, sets and/or weights, add a new exercise, etc. Continuing to increase the difficulty of your workout is key to keeping your body adapting and improving.

Sources: 
http://www.huffingtonpost.com/james-clear/forming-new-habits_b_5104807.html
http://www.mensfitness.com/training/pro-tips/how-long-do-you-need-work-out-see-results
https://www.livestrong.com/article/438047-how-long-does-it-take-to-change-your-body-after-working-out/