possible belt problem?needs help!

so recently when the weather has been getting colder when i start up my 01 forester it makes a loud screeching noice for about 5-10 seconds, i thought it was the belts and brought it to a shop and they said belts seemed fine and didnt make a noise because it wasnt cold at that time, any ideas? also it seems to buck sometimes when shifting or hesitate, automatic, help greatly appreciated...
thanks