ECM sets DTC P2106 to indicate ETC (Electronic Throttle Control)system malfunction has occurred and engine is in Limp-Home mode. The ECM reduces engine torque by 25% of normal value after setting the DTC, as an Emergency Operation(Limp-Home)mode.
If it's still under warranty there shouldn't be any cost.
If not, it's a crapshoot, but I'd take it to the dealer, or a well equipped shop that has diagnostic equipment. They will be better equipped to isolate the problem area.
Never tried it on the Kia, but next time it occurs, disconnect the negative battery for 30 seconds or so to see if it clears the history and returns to normal operation. If it does, it's only a short term fix, so better get it repaired.