Excel Not Responding

For the last couple months or so my users have been complaining about Excel not responding (See attachment) when they click into a cell from other apps.

It seems to be intermittent and freezes up the application that lasts less than a minute. They then can continue working on it again.

Not sure if its related to some MS updates that caused this problem or not.

Wondering if there are any other Excel users experiencing the same thing in their environment & possible solutions.

Thx