B737NG Captain reported experiencing a buffet and roll that may have been related to wake turbulence.

Narrative

Approaching FL330 during our climb out we experienced an unexpected aircraft buffet and roll. The autopilot (CMD B) and autothrottle were engaged; and we were climbing at Mach .79. The event began with aircraft buffeting that started light and increased to moderate; followed by the aircraft starting to roll to the left and then right. The First Officer who was the PF disconnected the autopilot; lowered the nose slightly which stopped our climb and began to regain positive aircraft control. The buffeting and rolling action stopped and we began our climb again only to encounter the same event again. This time we decided to descend the aircraft in which the buffeting and rolling actions stopped and we leveled at FL310. While descending to FL310 we received clearance from Center to level at FL310. Once level at FL310 the autopilot (CMD B) was re-engaged with no issues. The total event time was approximately 2 minutes. At this point we began to troubleshoot; there were no abnormal systems indications; engine indications; or annunciation lights. We transferred aircraft control and I disconnected the autopilot and autothrottle to feel the flight controls and how the aircraft was responding. Everything felt to be normal. We had the flight attendants take their jump seats at the beginning of the event; so at this point we had them check in. I utilized the function to get a patch through to Maintenance Control. I debriefed them on the event; they were unaware of any other similar events and believed it to have been a wake turbulence encounter. The First Officer and myself made the decision to continue the flight; but if we experienced the same event again to consider a landing at the nearest suitable airport. The remainder of the flight was uneventful; and roughly 10 minutes after the event we resumed our climb to our cruising altitude without further issues. Upon arrival into DEN I was still unsure on the cause of the event and felt it necessary to make an ELB (Electronic Log Book) report to have the aircraft inspected before a further flight. At the beginning of the event it felt like wake turbulence; after querying ATC the only aircraft above us was another B737; as well a B787 who was further ahead of us. As well there were no reported turbulence events in our vicinity. There was never an indication of a systems issue; however we both agreed the event to have seemed abnormal.