Outside temp. 15. veh. has 98,000 miles. Trans. just started to slip when starting to excellerate. have to use a lot of RPM to move vehicle. veh. had been sitting for approx. one week. no noticable problems prior.

It's worth a try. I would suggest Trans-X. Do a fluid and filter change and add 1 quart of Trans-X instead of a quart of fluid. Then drive the car on a road trip. Get about 100 miles on it and check the fluid level. The Trans-X is mostly solvent and will evaporate off rather quickly, say within the first week, and then top off the fluid. If it doesn't work, you will be looking at a rebuild or replacement with a good used unit.

get it serviced?
hard starts are usually never getting a tuneup, (like spark plugs?)
slamming in to gear is normal if RPM is too high in park, is it.
wont move , in any gear, car wont move even in reverse.
and RPM of engine does what , sticks low, like 800 rpm
or screams at the advancement of right foot.
need lots of details. we cant drive car, but if could in 5min flat all that is clear,
eg:
transmission slips
engine weak
engine racing in park too high.
wont start and misfires when it does.
is fuel fresh, not year old.
ever get a new air filter and fuel filter. if filter is outside tank.

Any slipping that you notice & RPM Flairs,the damage
is already done

You can not drive any vehicle more than 10 miles to home
or a shop, when they slip

Whatever was the start & cause of some of the problems,
now won't matter much, as there is a very good change you
will need to have the trans rebuilt

You could have a tran shop check it out,but it will
most likely have to come out to even get at any
solenoids,etc

I would say it's bad contacts in the ignition switch. Metals change dimensions depending on temperature, looks like 45 degrees is the trick point for whatever is in there. My 04 Silverado 5.3 with 196,000 has the ticking, but it is gone within 10-15 seconds.

Any slipping & you continuing to use it

I would just pull the trans & rebuild it

You want a trans shop,not a mechanic

replace temputer sensor it not telling the true temp to computer

Ya sounds like the electric shift solenoid. Problem with electrical. Will not give you a warning. Will go bad in a heartbeat. You can try unhooking plug that gos into the trans and spray electrical cleaner on it. plug back in. Wiggle some wires and maybe find one loose or broken wire or connection and hope for the best. But its probably the tranny with that many miles. Go to Advance Auto Parts they usually scan your car for free for codes. Good luck

either your cat has melted. Or your trans is shot

The clutch plates are grinding

tranny mite be slipping or getting hot... look at the tranny cooler to elimanate this possabilty