Unintentional mouse movements, am I paranoid?

I would suspect, first of all, optical/mechanical issues with the mouse.

Firstly, the optical sensor needs to be clean and free of grease (including invisible fingerprints), fluff and hair - on the outside and inside. This goes not just for the bit that lights up, but the sensor.

The optical unit is designed to focus at a specific distance, and if it is dislodged or adjusted in any way, then it can not work. I had a mouse where two of the stuck-on "feet" of the mouse came off, placing the optical sensor a very slight distance (fractions of millimetres) closer to the table/mousepad surface, making the mouse highly unreliable.

It could just be a dodgy mouse.

• An optical mouse could cause some erratic behavior if there is a hair or something stuck underneath it and triggering the sensor; remove the hair.

• A ball mouse can cause erratic behavior if there is dirt stuck to the rollers; clean the roller and ball.

• An wireless mouse can cause erratic behavior if there is interference between the mouse and the sensor; try a different channel or clear a line-of-sight between them.

• A wired mouse can cause erratic behavior if there is a bad connection, for example a frayed cord or cold-joint/broken solder connection on the PS/2 or USB connector; replace cord/mouse or use a different port.

In your specific case, it sounds like a recent problem and an intermittent one at that. Does it usually happen on the same day and/or at the same time? It sounds like some new device that is causing interference when it turns on. Have you installed any new electronic devices or appliances in the past few months? Have you gotten new neighbors or was there any recent construction?