Correct design of Colpitts oscillator
There is already an equivalent input series resistance.  Why would you think you need more? hFE Re = Rin.
The concept of the Colpitts Osc shown here is to amplify AC current &gt; 1 by series resonance in phase with output.  This would be a Series mode Crystal with low ESR and the Xtal is a RsCmLCp equivalent  circuit with C1,C2 added for tuning.
Here I have simulated a 10MHz Colpitts Osc with an added series Rs=10 that you may adjust with your mouse-wheel to determine how much gain margin you have before it stops oscillating.  This is how you validate the oscillator gain stability margin for a given series crystal oscillator.
This is time-averaged if the transistor ratios are overdriven into cutoff of base current, or may be tuned for small Vbe variations and a better sinewave out.