And sometimes when I try to open a second workbook, it will stall until I click on the File tab, on the open workbook. Then bam, it will open up.

Is it possible you were just entering information into a cell in the open workbook and didn't click enter or out of the cell? The only time Excel does that to me is due to the above. If so you don't have to click file but you do need to finish editing the cell value, either by clicking a different place in the worksheet hitting enter or clicking the menu like the file tab.