Cruising about 90 and all of the sudden,it felt like I went off the road. BAS/ESP light came on. Stopped & everything looked OK. When I started out, it felt like the RH rear brake was tapped ...twice. Made it home. Next day, everything worked fine ? ? ? What was that all about?:

 

it must be a malfunction.

esp can apply the brake to a certain wheel without the driver's intervention.

 

Also a diff in tyre diameter front to rear can give similar fault. Check for wear and/or tyre pressure problem.
error gets greater at speed.
Another thing can be an intermittant tone ring sensor or dirt in tone ring.

Bazzle