I feel your pain on the knees. Similar boat but not done anything to fix em yet. Got one of those creepers at the local W-Mart that converts to folding stool, quite handy with bad knees, rolls well on concrete, good value for home use. Watch for next time this issue crops up to see what is still working when that key is turned like if you had heater on last time is it still blowing or if radio was on and resumes play. If those items still operate it would help narrow down probable cause and find a solution. Example, if those items work maybe the transmission switch is faulty telling the computer truck is in gear and thus no crank on starter. A quick forum search on terms like no turnover or no crank/ no start gives quite a few hits with details on what was occurring and how they fixed it. Keep at it, let board know if you get it fixed and how, helps others in future.

You personally lean pretty strongly towards starter solenoid being the culprit of the no turn over condition. It’s not a costly part if want to eliminate that from the equation at avg of $20-$25. Seeing all the other items that are active when the key is in run does reduce the possible things to cause this. As I mentioned there is also a “sensor” that lets car know its in either park or neutral so its safe to turn over engine. Next time it occurs, try putting it in neutral and see if that changes status (I’m assuming automatic transmission). Seems to be less likely the ignition key tumbler at fault by noting everything else that did activate. Intermittent problems are a real hassle to fix, I know personally from experience when I was an electronic engineering technician that being able to duplicate the problem was half the battle so you could then find and apply the solution otherwise it’s best educated guess and process of elimination.

Simple answer yes. The contacts that close the circuit get carboned up from the electrical arc and conduct the electric flow poorly. The coil that energizes can have the windings deteriorate which pulls the contact with less force again results in poor electricial flow. Generally all of this and few other descriptions like the contact plate hangs or sticks when trying to close or open causes problems so repair wise most people just say its sticking or gone bad because they just do wear out. Add in the vibrations from driving, water and dirt, heat, cold - need I say more? Even the temperature or humidity can effect a part that’s compromised. Your issue is will not crank or turn over intermittently. So far sounds like a compromised selenoid/relay.
Thinking about it the number of times I have heard or read someone just tapping on a relay type part with a hammer gets it working for even a while is quite high. “Love tap” some would say.
At this point you could just go with you gut and replace the starter selenoid and see if problem stays away/fixed. It is not a real costly part or go on a limb and change out the whole starter/starter selenoid assembly. (Yes, starters can be intermittent too- electrical brushes on stator wear out, windings burn out, etc) If issue returns then you need to look elsewhere obviously at some other electrical item that is related to cranking the engine over. In the end it all amounts to time, money and effort which only you can determine. You can do it, questions ask- plenty of helpful folks here.