I had an x-700 new from '84 until three years ago, that was just fine until it and I went for a swim together. Then I replaced it with an x-570, which is like a brother to the x-700 without program ,and with better metering options in manual exposure modes. The first one exhibitted a similar problem to yours shortly after I got it.
It turned out that one of the two 'big' electrolytic capacitors in it were going. They are used to store energy from the comparatively small current limited battery to power the big current draws when the electromagnets that control the shutter curtain release. Replacing them is not a DIY fix; a professional fix is to replace them with tanatalum capacitors; which don't dry out/die nearly as readily. I elected to send it back and get another one.
Then I bought a second x-570 as a backup, I liked it so much better than the x-700, for when I shoot b&w.
To round out my options I bought a srt101 about 10 years ago, to share my MD glass optins with and there is very little electronic to have to worry about in it.