Battery wont stay charged

I have a 1995 Cirrus that has been running great for years until last month. I went to start it after work one night and it was dead. No turning over, no clicking sound, no door chimes, dead. I got a jump and when I tried to start it the next morning same problem. So I bought a new battery. This worked the next two times I started it and then dead again. So I took it to my mechanic. They ran diagnostics on the battery, alternator ect. and could find nothing wrong. They charged my battery for me and told me I needed to take it to the dealer. With the battery charged I drove home.
It sat for three days before I took it to the dealership. When I went to start it that morning it started right up. Of course the dealership found nothing wrong. It has been working fine for a month until Monday. Now I am having the same problem again. Here’s the lowdown:

-When starting no turning over, no clicking sound, no door chimes, dead.
-I can jump it and it runs.
-Once it is jumped the headlights and cruise control work normally.
-The gauges generally work but a couple times a minute they seem to loose power and flicker on and off.
-The radio loses power in sync with the gauges.

:banghead: :banghead: :banghead: :banghead:

new battery perhaps?

my battery died with no warning whatsoever. i was at a party and was sent to get water balloons for a massive water fight (irrelevant, yes, but im reliving the moment). i sat in the car, turned the key, nothing. not a sound. we tried jumping it with buddy's dads impala, nothing. my pa had to come with his monster van and we finally got enough of a charge to start it up, but the lights didn't work and the guages all flickered. so we changed the battery. we ended up needing to change the distributor too shortly after.

Maybe start with checking the terminals at both the battery and the jumping posts. Make sure they are clean and tight. Sometimes we overlook the simplest cures thinking the worst. I've been there and done that. If the car runs after a jump start, one could assume that the charging system is working and a possible battery or terminal problem. A weak battery or poor connection could power the ignition system for awhile but not deliver enough amperage to drive the starter motor, hence the clicking sound. With the battery replaced we can rule that out. And no alt light on, I'm thinking connections.....