Sounds either like the mirror lock up custom function has been enabled, or perhaps 2s or 10s self timer has been knocked on in drive mode.
The first is unlikely to have been hit by accident because you need to go into menus and submenus (I suppose it could theoretically happen if being knocked about in a bag...)
More likely you've been toggling drive modes. Both worth checking before you condemn the camera to a service.
Canon 7D, T3i, EOS M, EOS 3, GoPro HD Hero & Hero 2, powershot sx230 hs, Canon 70-200 f2.8 L, Canon 100mm f2.0, Sigma 70mm f2.8 Macro, Canon 50mm f1.8, Canon 22mm f2.0, Sigma 18-50 f2.8, Tokina 11-16 f2.8, Lensbaby Composer, Holga HL