Is it normal to be paranoid?

I get bouts of paranoia here and there. Instances where I feel like what I am doing is being monitored and that all my thoughts are being deciphered.
E.g. I would think about something, my own conversation with myself when suddenly a workmate repeats the exact same thing to me. Verbatim.
E.g. I carefully place something from a table on a shelf and 10 seconds later it is right back on the table.

I get wary about mentioning things out loud or keeping a record of thoughts as I feel like people can see and hear what I am doing.

Does this pertain to you? What should I do to stop being paranoid?