car is having trouble turning on

[Drummer829]

ok, so when the car is cold, when i turn the ignition to start the car, it almost sounds like the battery is dead (but its not). it gives a clicking sound when turning the key. after the 3rd or 4th time trying to turn it on, the car starts to vibrate and sluggishly turns on. It idles a little rough for the first few seconds and then runs like normal. After it is warm, I turned it off, and then turned it back on and it started perfectly. It still drives fine, it is just when it is cold and that initial turn of the key.

Oil was just changed and I alternate cars, so sometimes the car sits in the garage for 2-3 days before driven again. However, before the oil change, the car would sit for the same amount of time (maybe longer) and turn on without a problem

My guess is the spark plugs, but any help would be great as this is starting to worry me.