Computer Freezes in 20-30 sec Intervals

Recently, my computer has begun freezing. It happens with fair regularity, but does not seem to be tied to any particular schedule or event. I can be in any program typing (email, Word, Excel, anything) and suddenly the text stops appearing on the screen. I still have control of my mouse, I don’t get a blue screen, it doesn’t shut down on me. It only stays “frozen” for 20-30 sec at a time; and if I continue to type while it is frozen, the text will catch up and appear on the screen once it unfreezes.

I would appreciate any tips on this, it’s driving me crazy!

Thanks!