1996 Jeep Cherokee sometimes wont start

My jeep sometimes wont start. Its usually after its been sitting for a day or 2. When I try to start it it acts like the battery is almost dead, lugs and stuff. If I give it a lot of gas, it will turn over, but I have to keep the rpms up for about 10 minutes or drive it around while keeping the rpms up, otherwise it won't idle. I've had it in to 2 different shops and no one could figure it out. Like I said it doesn't happen all the time, usually just when it's been sitting, and when I do get it started it's fine. Thanks for your help.

jim