Excel taking an exorbitant amount of time to enter text into a cell.

I'm at my wits end here, Excel has become functionally unusable. I type text into a cell, hit enter to move to the cell below, and it essentially freezes. The text remains in the formula bar, but doesn't appear in the cell. I cannot select another cell, a tab, a function on a tab, or anything else except apparently the save button. I have to save the workbook, close it, and open it again, and the text is there. This has been an intermittent problem over the past few months, but it cleared after reopening the workbook after 3 or 4 tries. Now, I'm up to 10 times, and this issue is still with me. I'm begging anyone for help, please.