Peabody writes:

I have a kitchen and two bathrooms full of 4-foot fluorescent tubes. An
increasing number of fixtures don't turn on right away, but may turn on a few
minutes later. And all may work fine in cooler weather. Changing out the
tubes doesn't help.

The house was built in 1972, so it may just be time to replace the ballasts.
But I also wonder if it might be worth trying to reconnect the lines with new
wire nuts on the theory that the old ones just aren't making good connections
anymore unless the temperature is right.

Anyway, assuming I need to replace them, will I be able to find them at Home
Despot or Lowes? Is there anything in particular that I need to look for?
These are just standard 40-watt tubes, two per fixture.

You can buy LED replacements for those tubes.
They last forever, have a beautiful light color,
and use less electricity, start instantly.

Get the kind that does not need or use the existing
ballast. You need to open each fixture and rearrange
the wires. Very simple.

--
Dan Espen