EMB-175 Captain reported a flight control anomaly where the control column moved momentarily during cruise flight without an EICAS warning message in flight. The crew diverted to an alternate airport and landed safely overweight.

Narrative

I was the Captain on Aircraft X. Aircraft X operated from ZZZ1 to ZZZ2. In cruise flight no turbulence; north of ZZZ the control column snapped forward and back to neutral very quickly. I assume the column went forward around 30 percent of its half range with neutral being zero. It was very sudden but caught both pilot's attention. I currently have around 6000 hours in the EMB-170 series aircraft and never witnessed the control column act in this manner. The autopilot did not disconnect; there was no EICAS messages. It did appear to have slightly nosed down but it was so sudden it was barely noticeable. I did note before this anomaly occurred the trim was 3.0 and after was at 3.4. Right after this anomaly occurred I took the controls and disconnected the autopilot. I hand flew the aircraft for a few minutes and the aircraft handled normally. Note: Our cruise altitude was FL280 out of RVSM. I then discussed with my FO (First Officer) if this aircraft is safe to continue flight. We both agreed that it couldn't have been the autopilot with such a sudden movement. Worse case it could be an elevator issue electronically/ACE (Actuator Control Electronics); or hydraulic/PCU (Power Control Unit). We decided to be safe and land. Closest airport was ZZZ3 but that would have required a rapid descent. ZZZ4 was straight ahead and 100 NM. I was the flying pilot at this moment; First Officer got the FMS loaded and performance landing numbers. All checklist were ran; the approach was briefed. I briefed the passengers and cabin crew of the divert. The reason was a control anomaly and that the aircraft was operating normally; this is a precautionary diversion. I realized the aircraft was going to have an overweight landing. I then [requested priority handling] as per SOP. I had the choice to burn fuel below max landing weight or land overweight. I chose the latter; having a flight control issue. I landed the aircraft very smoothly. Pulled the aircraft off the runway and had the Airport Fire and Rescue check the aircraft. Note: An Autoflight Control System Fault Fail message did appear on the EICAS upon landing. I then taxied to the gate normally.Suggestions - I had a choice to continue or to land. After First Officer and I discussed worse case being a ACE or PCU problem; Autopilot malfunction or something as small as a channel failure and the backup transition was not the smoothest. I chose to land not knowing what the problem was leaning toward the safest option.