Excel selection of a cell

Hello

I am having trouble selecting a single cell on a worksheet. When I click in a cell, excel selects more than one cell at a time. Sometimes it will select three or more cells below the selection in addition to the cell I require (screen capture attached). In this image, I selected 4.728 and excel selected the two cells below. If I hold down the left-click I am able to scroll back to select the cell but it is very awkward. It does not matter how careful I am with the selection.

Is there a setting to prevent this happening. In AutoCAD, it is possible to reduce the size of the selection-cursor but I am unable to locate the adjustment. I have increased the size of the cells to 200% and the problem still occurs. The problem is intermittent but when it starts, it stays. Logging off and on again seems to solve the problem for a limited time.

Regards