skidding on variable pavement conditions

[Sh B]

I am increasingly nervous driving my 2013 Tahoe. It skids/swerves particularly when half the pavement is wet or icy or bumpy and the other half is dry. It does not stay on course and I have to slow down and correct steering. No indicator lights flash. This can happen any time, at speeds above approximately 20. Vehicles on the road around me under the same conditions are not skidding. All four tires are 5 months old (factory standard). I took my Tahoe to the dealership and they said it needed alignment. The problem persists despite alignment. How do you diagnose Stabilitrak malfunction? Traction control problem? Any insights/advice?