95 century intermittent starting/power problems

I have a 1995 buick century. The problem started several weeks ago. Nine out of ten times the car would crank right up, but on that tenth time when I turned the ignition all I would get is a single click. I would keep turning the ignition and it would finally crank after about eight tries.
As time went on that nine out of ten success rate dwindled down to a fifty-fifty chance of whether the car would crank or not. My friends told me I needed a starter solenoid. I bought one but I haven’t replaced it yet. (DO I HAVE TO REMOVE THE STARTER TO REPLACE THE SOLENOID? The repair manual says I have to but it looks like I can replace the solenoid without removing the starter.)
Recently the problem has become worse. It doesn’t happen often but every now and then when I try to crank the car I lose power. No horn, lights, radio, nothing. After waiting for 15 minutes to an hour the power would be restored and it would crank. Once I got it to crank after I jiggled the cables around the starter solenoid. That only worked once so I don’t know if that was a coincidence or not. I need help.
Thanks.

if the positive side of the battery has two cables stacked togeather,try cleaning and tightening. be sure to remove negative first and install last also leave lights on when cranking and check if they are dimming while cranking.