small red lights flash on my Nakamichi PA-7

These lights indicate clipping

but sometimes the small red lights on the front of the amp blink or stay on for a second

As Docdan50 stated, clipping, or the amp has reached maximum power output. An extremely quick blink that rarely happens is probably OK, however, the longer it stays on, the greater the chance for damage to happen, especially to the speaker. Sorry, but you will just need to turn the volume down slightly.

What speakers are you using?

I had one of those 'Naks years ago...and getting the clipping light to come on (300 watts pre side) meant things had become VERY loud, so if that's not the case then I'd get it checked out if possible.

I had one of those 'Naks years ago...and getting the clipping light to come on (300 watts pre side) meant things had become VERY loud

That may or may not be true, as it will depend on the sensitivity of the speaker and size of the room. Using a very low sensitivity speaker in a large room, it would be very easy for the clipping lights to come on, and not be very loud.

So again, what speakers are you using?

Those lights should be mandatory on ALL amps !
30 years ago they hipped me into just how much power Maggies
REALLY need, as in 500 watts a side into 4 ohms on up.