Apple logo and spinning wheel

i face the problem of apple logo and spinning wheel during startup quite often and dread to shutdown my mac. the machine has then always to be restored by time machine. i have upgraded to mavericks (not a clean install). what could be the reason of this problem.? some applications that have been installed? it is too frustrating to again always restore and also rebuilt outlook identity

You haven't given us any information about your Mac which makes it difficult to help you.

The spinning wheel could be related to a bad hard drive or it could mean your hard drive is almost full. Not enough memory, too many programs running at the same time, etc.

Tell us which Mac you have - year and model? Version of OS X it's running?