2000 vw golf rpm's rev without any prompting and car intermittently not starting

i have a manual 2000 vw golf with about 131.000 miles on it. the past month or so i have been at a stop or driving even and the rpm’s begin to increase without me touching the gas. sometimes ill be in neutral, sometimes ill be in gear, sometimes ill be at a light with the clutch pushed in. any ideas???

also, i have noticed when its hot outside this occurs more. also when it is hot outside the car is less likely to start. sometimes ill have driven the car, parked, run into someplace for less than 10 minutes–i come back and the car wont start. it takes a good 3-5 tries and pushing the gas in and it finally starts. this second problem of the car starting intermittently has been going on for about 1 year, i only notice it in the summer time. and it doesn’t happen more than 2-4 times per month.

any! ANY ANY!! suggestions or thoughts are welcome.

My instant reaction is vacuum leak. Check all the hoses and vacuum lines, including the big line to the brake booster, and the large air intake hoses. Check for cracks and loose lines.