have a wander around youtube .. try a few ideas and look for a class.
I try to meditate, but always seem to fall asleep once relaxed

Jon Kabat-Zinn has some good guided videos.I couldn't find the series but this one may be worth a try. They were around 20 or 30 minutes.

I have been doing Transcendental meditation since age 19. Took a meditation class at University of Michigan. The instructor gave me a mantra to repeat. "Ay-u-ma."

Over the years, I changed my mantra to "Let go." Let go of tension, worries, physical pain, monkey mind, etc. That's right for me.

"You're meditating wrong," a jackass medical doctor I met through online dating said. "Don't tell me how to meditate," I replied. He wanted me to sit in a lotus position. That's not relaxing.

My body temperature and heart rate decrease when I meditate, I learned through bio-feedback in my 30s.

So, I lie on the couch to relax, covered with a down throw. Repeat silently: "Let go, let go, let go..." Muscles and tension melt away. When I catch myself thinking (monkey mind), I don't chide myself. Instead I gently return to "Let go."

It takes 20-30 minutes. Sometimes I set a timer.

Feels like I'm floating in a trance. After 30 minutes, I gently "awaken," feeling relaxed, grounded and deeply refreshed.

I try to meditate every day.