B737NG Captain reported a wake turbulence encounter descending into IAH resulted in a slight track deviation.

Narrative

While descending into IAH on the DRLLR 5 arrival we experienced wake turbulence at DOMNO. The autopilot initiated the desired left turn but at less than 5 degrees of left bank; the aircraft suddenly rolled right to approximately 20 degrees of right bank. The autopilot remained engaged and immediately corrected back to a left turn to the correct course. The short delay in the turn caused us to go approximately 1 mile off course. ATC noticed and asked if we were going direct to ZOEEE. When I reported to them that we had experienced wake turbulence. I initially used the term 'severe'. When they asked me to confirm that it was severe turbulence I corrected it to 'strong but not severe'. It wasn't so much the strength of the turbulence but the sudden nature and the fact that it occurred exactly when we should have been turning left. I doubt anyone in the back of the aircraft even noticed. ATC asked me to call them after landing and provided a phone number. After landing I called and their only question was if there were any injuries. I told them there were none and reiterated that my initial statement of 'severe' was incorrect. The event was actually very mild; just poorly timed. Additionally; I am using the term 'wake' turbulence because it felt like every other wake turbulence encounter I have had; but I don't recall there being an aircraft in front of us on the arrival. We were eventually vectored behind [another aircraft] on final; but I'm not sure what arrival that aircraft came from.