1999 expdetion (first time poster)

I was out driving around and swung in to a parker spot pretty fast. Popped in park, turned it off and jumped out. Ran into a store for 2 minutes and came out and it wont start.
lights, windows, radio.....all work fine, but when you turn the key, you get nothing but a one little click noise from under the dash. That is it.

it is parked on a slight down hill.

if there some kind of sensor that thinks i am about to tip over? (stopped short and leaning forward too far?)

worth disconnecting the battery and resetting the system?

whats clicking is the relay under the dash. sometimes it clicks when theres a loose ground or something, also have you checked the fuses?

hey i have a 99 expdetion and i 2 problems 1 its very rough and i got to rev it up and 2 theres a code i forget the number but its shift solenoid and i dont know where i would start to look for it any ideas?